Characterization of the cytochrome bc1 complex pet genes from chromatium vinosum

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Title: Characterization of the cytochrome bc1 complex pet genes from chromatium vinosum
Author: Chen, Yie Lane
Abstract: This research is focused on three different regions of the genome of the purple sulfur bacterium Chromatium vinosun : (1 ) Characterization of the pet operon , coding for the three subunits of the cytochrome bc1 complex of C vinosum , (2 ) Characterization of the ccll and helX genes encoding cytochrome c heme lyase and a thioredoxin -like protein of C . vinosum , respectively . These two gene products are essential for cytochrome e biogenesis . (3 ) Characterization of C vinosumpurH , IpxA , and purD genes encoding the bifunctional enzyme 5' -phosphoribosyl 5 -aminoimidazole -4 -carboxamide (AICAR ) formyltransferase /GMP cyclohydrolase , the UDP -iV -acetylglucosamine O -acyltransferase , and the 5’ -phosphoribosyl -glycinamide (GAR ) synthetase , respectively . Both the purH and purD gene products are essential for purine biosynthesis . The IpxA gene product is essential for lipid A biosynthesis . Ubiquinol : cytochrome elc2 oxidoreductase , also known as the cytochrome bcj complex , is a membrane -bound protein with multiple subunits that is widely distributed among diverse families of organisms . It is present in eukaryotic mitochondria for respiratory electron transport , and in photosynthetic bacteria and aerobic bacteria for photosynthetic electron transport or respiratory electron transport . This enzyme catalyzes electron flow from ubiquinol to cytochrome c (ci ) generating a proton gradient which is coupled to ATP production and other processes involved in energy utilization . In this work , portions of the structural genes for the Rieske iron -sulfur protein and cytochrome b subunits of the cytochrome bci complex of C . vinosum have been cloned and both strands sequenced . The organization of the genes coding for the prosthetic group -containing subunits of the C . vinosum cytochrome bci complex is similar to that reported previously for the pet operon of photosynthetic purple non -sulfur bacteria . The amino acid sequence deduced from partial sequences of the petAB genes show homology to the Rieske iron sulfur proteins and cytochrome b subunits of photosynthetic purple non -sulfur bacteria . Cytochrome c heme lyase catalyzes the ligation of heme to apocytochrome c during cytochrome c biogenesis . The thioredoxin -like protein maintains the cysteine residues of apocytochrome c in their reduced state for heme ligation . Portions of the sturctural gene for the cytochrome c heme lyase and the full -length gene for the thioredoxin -like protein of C . vinosum have been cloned and both strands sequenced . The deduced amino acid sequence of the C vinosum cell gene shows homology to the corresponding protein encoded by Rb . capsulatus ceil gene , the protein encoded by E . coli cemF (yejR ) gene , the protein encoded by the H influenzae cemF gene , the cycK gene product ofB . japonicum , R . meliloti , and R . leguminosarum , and the cyt4 gene product of Pseudomonas fluorescens . The deduced amino acid sequence of the helX gene of C vinosum shows homology to the corresponding thioredoxin -like proteins encoded by the Rb . capulatus helX gene , the B . japonicum tlpB gene , the E . coli cemG iyejQ ) gene , the P . fluorescens cyt5 gene , the H . influenzae dsel and dse2 genes , and the K leguminosarum cycY gene The purH gene product catalyzes both step 9 and step 10 of the purine nucleotide biosynthesis . The IpxA gene product catalyzes the first step of lipidA biosynthesis . The purD gene product catalyzes the second step of the purine nucleotide biosynthesis . Portions of the C vinosum purH gene , the full -length IpxA gene , and portions of the purD gene have been cloned and both strands sequenced . The C . vinosum purH gene shows homology to the purH gene of £• . coli and Salmonella typhimurium at both the nucleotide and deduced amino acid levels . The IpxA gene of C vinosum shows homology to the IpxA gene of 5 . typhimurium , E . coli . Yersinia enterocoeitica , and Rickettisia rickettsii at both the nucleotide and deduced amino acid levels . The purD gene of C vinosum shows homology to the purD gene ofE . coli and S . typhimurium at both the nucleotide and deduced amino acid levels .
URI: http : / /hdl .handle .net /2346 /16463
Date: 1996-08

Citation

Characterization of the cytochrome bc1 complex pet genes from chromatium vinosum. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /16463 .

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