Flavocytochrome <I>c</I> from the Gram-negative bacterium <I>Shewanella</I> <I>putrefaciens</I> is a soluble, periplasmic fumarate reductase induced under anaerobic conditions. In order to study this protein the entire structural gene was cloned and sequenced, along with some surrounding sequence. Analysis of the cloned gene indiciates that flavocytochrome <I>c </I>consists of 571 amino acids preceded by a putative periplasmic signal sequence of 25 amino acids. Flavocytochrome <I>c</I> appears to consist of two domains: -a cytochrome domain consisting of approximately the first 117 amino acids containing the four <I>c</I>-type haem binding motifs (CxxCH), which shows some similarity to a tetrahaem cytochrome from the purple phototrophic bacterium <I>H-1-R </I>-a flavin domain comprising the remainder of the protein which shows significant similarity to the flavoprotein subunits of the family containing fumarate reductases and succinate dehydrogenases from other organisms. For example, it shows 26% identity to the flavoprotein subunit of <I>Escherichia coli</I> fumarate reductase at the amino acid level, including all the active site residues which have been identified. Three additional open reading frames have been identified in the regions flanking the <I>fcc</I> gene. ORF2, is situated -400bp downstream of <I>fcc</I> and reads in the same direction as the <I>fcc</I> gene. The deduced amino acid sequence of this open reading frame is 135 amino acid residues in length and shows some limited sequence similarity for FrdD, one of the two subunits of <I>E. coli</I> fumarate reductase which serves to anchor the enzyme to the membrane and is involved in electron transport to the catalytic domain. Since flavocytochrome <I>c</I> is a soluble enzyme, the product of ORF2 does not appear to be a membrane anchor for this enzyme, however a role in electron transport to flavocytochrome <I>c </I>has not been ruled out. ORFI and ORF3 both read in the opposite direction from flavocytochrome <I>c </I>and neither is completely contained on the cloned fragment. Searching of the databases has revealed no apparent homologues for either of these reading frames.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:660478 |
| Date | January 1994 |
| Creators | Pealing, Sara L. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15615 |
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