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Structure-Function Studies on Aspartate Transcarbamoylase and Regulation of Pyrimidine Biosynthesis by a Positive Activator Protein, PyrR in Pseudomonas putida

Description: The regulation of pyrimidine biosynthesis was studied in Pseudomonas putida. The biosynthetic and salvage pathways provide pyrimidine nucleotides for RNA, DNA, cell membrane and cell wall biosynthesis. Pyrimidine metabolism is intensely studied because many of its enzymes are targets for chemotheraphy. Four aspects of pyrimidine regulation are described in this dissertation. Chapter I compares the salvage pathways of Escherichia coli and P. putida. Surprisingly, P. putida lacks several salvage enzymes including nucleoside kinases, uridine phosphorylase and cytidine deaminase. Without a functional nucleoside kinase, it was impossible to feed exogenous uridine to P. putida. To obviate this problem, uridine kinase was transferred to P. putida from E. coli and shown to function in this heterologous host. Chapter II details the enzymology of Pseudomonas aspartate transcarbamoylase (ATCase), its allosteric regulation and how it is assembled. The E. coli ATCase is a dodecamer of two different polypeptides, encoded by pyrBI. Six regulatory (PyrI) and six catalytic (PyrB) polypeptides assemble from two preformed trimers (B3) and three preformed regulatory dimers (I2) in the conserved 2B3:3I2 molecular structure. The Pseudomonas ATCase also assembles from two different polypeptides encoded by pyrBC'. However, a PyrB polypeptide combines with a PyrC. polypeptide to form a PyrB:PyrC. protomer; six of these assemble into a dodecamer of structure 2B3:3C'2. pyrC' encodes an inactive dihydroorotase with pyrB and pyrC' overlapping by 4 bp. Chapter III explores how catabolite repression affects pyrimidine metabolism. The global catabolite repression control protein, Crc, has been shown to affect pyrimidine metabolism in a number of ways. This includes orotate transport for use as pyrimidine, carbon and nitrogen sources. Orotate is important because it interacts with PyrR in repressing the pyr genes. Chapter IV describes PyrR, the positive activator of the pyrimidine pathway. As with other positive activator proteins, when pyrimidine nucleotides are depleted, PyrR binds to ...
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Date: December 2003
Creator: Kumar, Alan P.
Partner: UNT Libraries

Formation of P{sup +}Q{sub B}{sup -} via B-branch electron transfer in mutant reaction centers.

Description: The crystallographic observation of two symmetry-related branches of electron transfer cofactors in the structure of the bacterial reaction center (RC) 13 years ago [1] remains an enigma in light of experimental observations that show that only the A branch is active in the initial electron transfer steps in wild-type RCs. Unidirectional electron flow has been attributed to localized asymmetries between the A and B branches that lead to differences in: (1) the electronic couplings of the cofactors [2]; (2) the relative electrostatic environments of the cofactors, caused by amino acid differences which modulate the free energies of their charge-separated states [3] and/or create a higher dielectric constant on the active side, resulting in a stronger static field for stabilizing A-branch charge transfer states [4,5]. Some photo-induced bleaching of H{sub B} has been observed, in wild-type RCs following trapping of HA{sub A}{sup {minus}}[6], and in ''hybrid'' RCs where the redox potentials of cofactors were manipulated by pigment exchange [7] or mutagenesis [8]. Transient bleaching of the 530-nm band of H{sub B} was more easily observed in the hybrid RCs because the H{sub A} transition at 545 nm was shifted to {approximately}600 nm due to incorporation of a bacteriochlorophyll, designated ''{beta}'', at the H{sub A} site. No experiments to detect further electron transfer to Q{sub B} were done with either type of modified RCs. Many site-specific mutagenesis experiments have given us insight into the nature and magnitude of the effects that amino acid side chains can exert in tuning the relative energy levels of the cofactors to optimize the balance between forward and reverse reactions, and the large distances through which some of these effects are manifested. In this paper, we show that in mutant RCs of Rhodobacter capsulatus, P{sup +}Q{sub B}{sup {minus}} can be formed in the absence of prior formation ...
Date: August 14, 1998
Creator: Laible, P. D.
Partner: UNT Libraries Government Documents Department

Catalytic activity of nuclease P1: Experiment and theory

Description: Nuclease P1 from Penicillium citrinum is a zinc dependent glyco-enzyme that recognizes single stranded DNA and RNA as substrates and hydrolyzes the phosphate ester bond. Nuclease Pl seems to recognize particular conformations of the phosphodiester backbone and shows significant variation in the rate of hydrolytic activity depending upon which nucleosides are coupled by the phosphodiester bond. The efficiency of nuclease Pl in hydrolyzing the phosphodiester bonds of a substrate can be altered by modifications to one of the substrate bases induced by ionizing radiation or oxidative stress. Measurements have been made of the effect of several radiation induced lesions on the catalytic rate of nuclease Pl. A model of the structure of the enzyme has been constructed in order to better understand the binding and activity of this enzyme on various ssDNA substrates.
Date: October 1, 1994
Creator: Miller, J.H.; Falcone, J.M.; Shibata, M. & Box, H.C.
Partner: UNT Libraries Government Documents Department

Dysregulation of temperature and liver cytokine gene expression in immunodeficient wasted mice

Description: Wasted mice bear the spontaneous autosomal recessive mutation wst/wst; this genotype is associated with weight loss beginning at 21 days of age, neurologic dysfunction, immunodeficiency at mucosal sites, and increased sensitivity to the killing effects of ionizing radiation. The pathology underlying the disease symptoms is unknown. Experiments reported here were designed to examine thermoregulation and liver expression of specific cytokines in wasted mice and in littermate and parental controls. Our experiments found that wasted mice begin to show a drop in body temperature at 21-23 days following birth, continuing until death at the age of 28 days. Concomitant with that, livers from wasted mice expressed increased amounts of mRNAs specific for cytokines IL,6 and IL-1, the acute phase reactant C-reactive protein, c-jun, and apoptosis-associated Rp-8 when compared to littermate and parental control animals. Levels of {beta}-transforming growth factor (TGF), c-fos, proliferating cell nuclear antigen (PCNA), and ornithine amino transferase (OAT) transcripts were the same in livers from wasted mice and controls. These results suggest a relationship between an acute phase reactant response in wasted mice and temperature dysregulation.
Date: April 25, 1995
Creator: Libertin, C. R.; Ling-Indeck, L.; Weaver, P.; Chang-Liu, Chin-Mei; Strezoska, V.; Heckert, B. et al.
Partner: UNT Libraries Government Documents Department

Enzyme catalysts for a biotechnology-based chemical industry. Quarterly progress report, April 1--June 28, 1996

Description: The goal of this research is to engineer enzymes to be efficient and economically attractive catalysts for the chemical industry. The author is attempted to demonstrate generally-applicable approaches to enzyme improvement as well as develop specific catalysts for potential industrial application. The paper describes the progress in two projects: (a) Random mutagenesis of pNB esterase: Improved activity and stability; and (2) Subtilisin mutants exhibiting improved ligase activity in organic solvents.
Date: July 22, 1996
Creator: Arnold, F.H.
Partner: UNT Libraries Government Documents Department

Structural mechanisms of nonplanar hemes in proteins

Description: The objective is to assess the occurrence of nonplanar distortions of hemes and other tetrapyrroles in proteins and to determine the biological function of these distortions. Recently, these distortions were found by us to be conserved among proteins belonging to a functional class. Conservation of the conformation of the heme indicates a possible functional role. Researchers have suggested possible mechanisms by which heme distortions might influence biological properties; however, no heme distortion has yet been shown conclusively to participate in a structural mechanism of hemoprotein function. The specific aims of the proposed work are: (1) to characterize and quantify the distortions of the hemes in all of the more than 300 hemoprotein X-ray crystal structures in terms of displacements along the lowest-frequency normal coordinates, (2) to determine the structural features of the protein component that generate and control these nonplanar distortions by using spectroscopic studies and molecular-mechanics calculations for the native proteins, their mutants and heme-peptide fragments, and model porphyrins, (3) to determine spectroscopic markers for the various types of distortion, and, finally, (4) to discover the functional significance of the nonplanar distortions by correlating function with porphyrin conformation for proteins and model porphyrins.
Date: May 1, 1997
Creator: Shelnutt, J.A.
Partner: UNT Libraries Government Documents Department

Role of zein proteins in structure and assembly of protein bodies and endosperm texture. Progress report and appendix 1 - preliminary data

Description: Although funding for this project was initiated less than two years ago, we have made significant progress with our research objectives. We have cloned the gene responsible for the fl2 mutation. In fl2, the mutant phenotype appears to result from a defective signal peptide in an alpha-zein protein. As a consequence, the signal peptide remains attached when the protein accumulates in the protein body. A mutation like fl2 could explain other semidominant and dominant opaque mutants on the basis of abnormal zein polypeptides. A manuscript describing the research that led to the cloning of fl2 is in press, and a second manuscript on the characterization of this gene has been prepared for publication. We found that increased amounts of the 27-kD gamma-zein protein enlarge the proportion of vitreous endosperm and increases the hardness of o2 mutants. This protein also enhances these properties in wild type seeds. The mechanism by which the gamma-zein protein brings about these changes is unclear, and is under investigation. We have found and characterized several mutants that reduce gamma-zein synthesis. The mutations do not significantly affect synthesis of any other type of zein protein. They appear to create an opaque phenotype by reducing the number rather than the size of protein bodies. Interestingly, the mutant seeds fail to germinate. A manuscript describing one of these mutants, o15, has been prepared for publication. We have created a number of transgenic tobacco plants that can produce alpha-, beta-, gamma(27-kD)-, or delta-zeins, as well as combinations of these proteins. Analysis of seeds from these plants and crosses of these plants has shown that tobacco endosperm can serve as a heterologous system to study zein interactions. We have obtained evidence that interactions between alpha- and gamma-zein proteins are required for stable accumulation of alpha-zeins in the endosperm. These and other ...
Date: May 1, 1997
Creator: Larkins, B.
Partner: UNT Libraries Government Documents Department

Health hazards associated with the use of di-(2-ethylhexyl) phthalate (commonly referred to as DOP) in HEPA filter test

Description: Di-(2-ethylhexyl) phthalate (DEHP), commonly referred to as di-octyl phthalate, is an important production chemical in the US. In addition to its major use as an additive in plastics, DEHP is widely used to evaluate the effectiveness of high efficiency particulate air (HEPA) filters. Historically, DEHP was also used in quantitative fit testing for respirators. Evaluations of this compound a decade ago showed that it can induce hepatocellular carcinomas in laboratory animals. Although most Department of Energy (DOE) facilities have since discontinued using DEHP in respirator fit testing, DEHP continues to be used for evaluating HEPA filters. This report summarizes available information on the toxicity, mutagenicity, carcinogenicity, and other hazards and problems posed by DEHP, specifically with reference to HEPA filter testing. Information on work practice improvements as well as the availability and suitability of DEHP substitutes are also presented. This material should assist the DOE in the safe use of this material.
Date: January 1, 1995
Partner: UNT Libraries Government Documents Department

Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

Description: Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.
Date: November 8, 1999
Creator: Zheng, Junwei
Partner: UNT Libraries Government Documents Department

Porphyrin Interactions with Wild Type and Mutant Mouse Ferrochelatase

Description: Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the heme biosynthetic pathway, catalyzes Fe<sup>2+</sup> chelation into protoporphyrin IX. Resonance Raman and W-visible absorbance spectroscopes of wild type and engineered variants of murine ferrochelatase were used to examine the proposed structural mechanism for iron insertion into protoporphyrin by ferrochelatase. The recombinant variants (i.e., H207N and E287Q) are enzymes in which the conserved amino acids histidine-207 and glutamate-287 of murine ferrochelatase were substituted with asparagine and glutamine, respectively. Both of these residues are at the active site of the enzyme as deduced from the Bacillus subtilis ferrochelatase three-dimensional structure. Addition of free base or metalated porphyrins to wild type ferrochelatase and H207N variant yields a quasi 1:1 complex, possibly a monomeric protein-bound species. In contrast, the addition of porphyrin (either free base or metalated) to E287Q is sub-stoichiometric, as this variant retains bound porphyrin in the active site during isolation and purification. The specificity of porphyrin binding is confirmed by the narrowing of the structure-sensitive resonance Raman lines and the vinyl vibrational mode. Resonance Raman spectra of free base and metalated porphyrins bound to the wild type ferrochelatase indicate a nonplanar distortion of the porphyrin macrocycle, although the magnitude of the distortion cannot be determined without first defining the specific type of deformation. Significantly, the extent of the nonplanar distortion varies in the case of H207N- and E287Q-bound porphyrins. In fact, resonance Raman spectral decomposition indicates a homogeneous ruffled distortion for the nickel protoporphyrin bound to the wild type ferrochelatase, whereas both a planar and ruffled conformations are present for the H207N-bound porphyrin. Perhaps more revealing is the unusual resonance , 3 Raman spectrum of the endogenous E287Q-bound porphyrin, which has the structure-sensitive lines greatly upshifted relative to those of the free base protoporphyrin in solution. This could be interpreted as an equilibrium ...
Date: May 19, 1999
Creator: Ferreira, Gloria C.; Franco, Ricardo; Lu, Yi; Ma, Jian-Guo & Shelnutt, John A.
Partner: UNT Libraries Government Documents Department

Empirical potentials for recombination reactions of photo-dissociated ligands. Final report

Description: The aim of this research was to design an appropriate potential and simulation methodology to describe the effect of radiation on ligands bound to metal-proteins. As model systems the authors investigated myoglobin, hemoglobin and their mutants. The great advantage of the globins as a target for theoretical studies is the wealth of experimental data available for them. They focused on studies that combine fast spectroscopy with mutation experiments. The mutations make it possible to examine detailed changes in the kinetic curves with atomically detailed information. The first spectroscopy, which is in the same time scale as of ordinary molecular dynamics (sub nanoseconds), makes it possible to compare the results of the computations to raw experimental data.
Date: December 1, 1998
Creator: Elber, R.
Partner: UNT Libraries Government Documents Department

Final Report: Comparative Studies in the Field of Mouse and Human Leukemia, June 1, 1991 - October 31, 1994

Description: Early in the work on this grant the authors established that the growth factor-dependence of radiation-induced thymic leukemia cells was dependent on the autocrine/paracrine growth factor IL-4. Localized, thymic leukemias always grew by virtue of an IL-4-driven autocrine/paracrine pathway. They continued and investigated the mechanism of progression of the thymic leukemias to the later, disseminate disease. Linking the generation of disseminated leukemias to their growth factor-dependent status [10,11], they found that the development of growth factor-independence was associated with the dissemination of the leukemia from the thymus to other sites, e.g. spleen, lymphnodes, liver and kidney [9,8]. Indeed, all disseminated leukemias were composed of growth factor-independent cells. The generation of disseminated radiation-induced leukemia is associated with the loss of specific differentiation antigens and the mutation of the p53 tumor suppressor gene. The thymic, growth factor-independent leukemia carried non-mutated, wild type p53 [4]. These results suggested that it might be possible to influence the dissemination [6,7] of leukemia cell propagation in vivo by the re-introduction of wild type p53 into the leukemias cells. They could show that the transduction of genes encoding specific mutant p53 proteins enhanced their dissemination potential and, in addition, the transduction of constructs encoding wild type p53 reversed the disseminated phenotype--and the leukemic phenotype--of murine and human acute leukemia cells. As a result of the DOE grant, and to further study the gene-transduction approach for the inhibition of leukemia and other cancer cells, they developed an acute retroviral gene transfer system that was capable of the rapid generation of high-titer retroviral virions that were non-mutated and non-deleted [12]. This system has been supplied to dozens of laboratories in the country and is widely used in many research laboratories.
Date: December 1, 1998
Creator: Haas, Martin
Partner: UNT Libraries Government Documents Department

The iojap gene in maize

Description: The classical maize mutant iojap (Iodent japonica) has variegated green and white leaves. Green sectors have cells with normal chloroplasts whereas white sectors have cells where plastids fail to differentiate. These mutant plastids, when transmitted through the female gametophyte, do not recover in the presence of wild type Iojap. We cloned the Ij locus, and we have investigated the mechanism of epigenetic inheritance and phenotypic expression. More recently, a modifier of this type of variegation, ''Inhibitor of striate'', has also been cloned. Both the iojap and inhibitor of striate proteins have homologs in bacteria and are members of ancient conserved families found in multiple species. These tools can be used to address fundamental questions of inheritance and variegation associated with this classical conundrum of maize genetics. Since the work of Rhoades there has been considerable speculation concerning the nature of the Iojap gene product, the origin of leaf variegation and the mechanism behind the material inheritance of defective plastids. This has made Iojap a textbook paradigm for cytoplasmic inheritance and nuclear-organellar interaction for almost 50 years. Cloning of the Iojap gene in maize, and homologs in other plants and bacteria, provides a new means to address the origin of heteroplastidity, variegation and cytoplasmic inheritance in higher plants.
Date: December 1, 2001
Creator: Martienssen, Robert
Partner: UNT Libraries Government Documents Department

Final Report: Latent Expression of Genetic Damage in Human Lung Cells

Description: This project was aimed at furthering understanding of the latent effects of ionizing radiation. The underlying premise was that such latent (i.e., delayed) effects stemmed from radiation-induced genetic instability. As model system to investigate certain aspects of genomic instability, they proposed to look at chromosomal instability involving quasi-targeted radiation-induced breakpoints in the vicinity of the HPRT gene in EJ30 human epithelial cells. Using whole chromosome painting of the X chromosome, the authors were able to show that about 15% of randomly selected 6-thioguanine resistant (6TG{prime}) mutants involved translocations in the terminal portion of Xq. Subsequent analysis, using human genomic YAC probes confirmed that all the translocations were either within (or near Xq26.1), the cytogenetic location of HPRT, whereas none were found elsewhere involving the X chromosome.
Date: February 28, 1999
Creator: Cornforth, Michael N.
Partner: UNT Libraries Government Documents Department

Modified cellulose synthase gene from 'Arabidopsis thaliana' confers herbicide resistance to plants

Description: Cellulose synthase ('CS'), a key enzyme in the biosynthesis of cellulose in plants is inhibited by herbicides comprising thiazolidinones such as 5-tert-butyl-carbamoyloxy-3-(3-trifluromethyl) phenyl-4-thiazolidinone (TZ), isoxaben and 2,6-dichlorobenzonitrile (DCB). Two mutant genes encoding isoxaben and TZ-resistant cellulose synthase have been isolated from isoxaben and TZ-resistant Arabidopsis thaliana mutants. When compared with the gene coding for isoxaben or TZ-sensitive cellulose synthase, one of the resistant CS genes contains a point mutation, wherein glycine residue 998 is replaced by an aspartic acid. The other resistant mutation is due to a threonine to isoleucine change at amino acid residue 942. The mutant CS gene can be used to impart herbicide resistance to a plant; thereby permitting the utilization of the herbicide as a single application at a concentration which ensures the complete or substantially complete killing of weeds, while leaving the transgenic crop plant essentially undamaged.
Date: October 11, 2000
Creator: Somerville, Chris R. & Scieble, Wolf
Partner: UNT Libraries Government Documents Department

Final technical report [Molecular genetic analysis of biophotolytic hydrogen production in green algae]

Description: The principal objective of this project was to identify genes necessary for biophotolytic hydrogen production in green algae, using Chlamydomonas reinhardtii as an experimental organism. The main strategy was to isolate mutants that are selectively deficient in hydrogen production and to genetically map, physically isolate, and ultimately sequence the affected genes.
Date: December 31, 2000
Creator: Mets, Laurens
Partner: UNT Libraries Government Documents Department

Development of More Effective Biosurfactants for Enhanced Oil Recovery

Description: The objectives of this were two fold. First, core displacement studies were done to determine whether microbial processes could recover residual oil at elevated pressures. Second, the importance of biosurfactant production for the recovery of residual oil was studies. In these studies, a biosurfactant-producing, microorganisms called Bacillus licheniformis strain JF-2 was used. This bacterium produces a cyclic peptide biosurfactant that significantly reduces the interfacial tension between oil and brine (7). The use of a mutant deficient in surfactant production and a mathematical MEOR simulator were used to determine the major mechanisms of oil recovery by these two strains.
Date: January 16, 2003
Creator: McInerney, J.J.; Han, S.O.; Maudgalya, S.; Mouttaki, H.; Folmsbee, M.; Knapp, R. et al.
Partner: UNT Libraries Government Documents Department

Dissection of Molecular Mechanisms Regulating Protein Body Formation in Maize Endosperm - DE-FG03-95-ER20183 B139

Description: Dissection of Molecular Mechanisms Regulating Protein Body Formation in Maize Endosperm - DE-FG03-95-ER20183 Final Technical Report and Patent Summary Dr. Brian A. Larkins, Department of Plant Sciences, University of Arizona, Tucson, AZ 85721 Endosperm texture is an important quality trait in maize, as it influences the shipping characteristics of the grain, its susceptibility to insects, the yield of grits from dry milling, energy costs during wet milling, and the baking and digestibility properties of the flour. There appears to be a causal relationship between kernel hardness and the formation of zein-containing protein bodies, as mutations affecting protein body number and structure are associated with a soft, starchy kernel. In this project we used a variety of approaches to better understand this relationship and investigate the molecular and biochemical changes associated with starchy endosperm mutants. We characterized the distribution of zein mRNAs on endosperm rough endoplasmic reticulum (RER) membranes and the interactions between zein proteins, as each of these could influence the structure of protein bodies. Based on in situ hybridization, mRNAs encoding the 22-kD alpha- and 27-kD gamma-zeins are randomly distributed on RER; hence, mRNA targeting does not appear to influence the formation of protein bodies. Investigation of the interactions between zein proteins (alpha, beta, gamma, delta) with the yeast two-hybrid system showed that interactions between the 19- and 22-alpha-zeins are relatively weak, although each of them interacted strongly with the 10-kD delta-zein. Strong interactions were detected between the alpha- and delta-zeins and the 16-kD gamma- and 15-kD beta-zeins; however, the 50-kD and 27-kD gamma-zeins did not interact detectably with the alpha- and delta-zein proteins. The NH2- and COOH-terminal domains of the 22-kD alpha-zein were found to interact most strongly with the 15-kD beta- and 16-kD gamma-zeins, suggesting the 16-kD and 15-kD proteins bind and assemble alpha-zeins in protein bodies. ...
Date: March 21, 2003
Creator: Larkins, Brian A.
Partner: UNT Libraries Government Documents Department

Anaerobic Fe(III) reduction by Shewanella putrefaciens: Analysis of the electron transport chain

Description: The goals of the project were to isolate mutants that are deficient in metal reduction, identify components of the electron transport chain that are involved in this process, and purify some of these proteins for biochemical analyses. In the 3-year period since the start of the project, we have accomplished many of these goals. We have isolated several new S. oneidensis mutants that are deficient in metal reduction, and have initiated the development of vectors for the overexpression of cytochromes and other proteins in S. oneidensis. We have also overexpressed CymA, one of the c cytochromes that are involved in metal reduction.
Date: January 20, 2004
Creator: Saffarini, Daad
Partner: UNT Libraries Government Documents Department

DOE Final report [A genetic analysis of the lumenal proteins of the PSII O{sub 2} evolving complex of cyanobacteria]

Description: The primary objectives of this proposal were a better understanding of the structure and function of the Mn-stabilizing (MSP) in two cyanobacteria, Synechocystis sp. PCC6803 and Cyanothece sp. ATCC51142. In addition, the author was interested in analysis of the other cyanobacteria lumenal PSII proteins, cyt c{sub 550} and the 12 kDa protein. The experimentation involved analysis of targeted random mutagenesis of the genes encoding the three proteins, especially in psbO, the gene encoding MSP. This required mutant screening with a digital imaging spectrometer. Knockout mutants of the other two lumenal proteins in Synechocystis sp. PCC6803 were also constructed. In addition, photosynthetic O{sub 2} evolution in Cyanothece sp. ATCC51142, a nitrogen-fixing strain that regulates the activity of nitrogenase and photosynthesis in a temporal fashion, was analyzed.
Date: March 1, 2001
Creator: Sherman, Louis A.
Partner: UNT Libraries Government Documents Department