Biomaterial Database

Cobalamin (vitamin B(12)) biosynthesis in Rhodobacter capsulatus. 2002

H McGoldrick, and E Deery, and M Warren, and P Heathcote

Queen Mary, University of London, London E1 4NS, UK. H.M.McGoldrick@qmul.ac.uk

In Rhodobacter capsulatus, cobalamin biosynthesis has been shown to occur when the bacteria are grown either aerobically or anaerobically. However, a comparison of the main cobalamin biosynthetic operon found within R. capsulatus would suggest that the encoded proteins belong to the oxygen-dependent pathway for cobalamin biosynthesis, although, significantly, no homologue of the essential mono-oxygenase CobG has yet been detected. Nonetheless, within this main cob operon is found a large open reading frame termed orf663 that is not found in any other cobalamin biosynthetic operon. When overproduced in Escherichia coli, orf663 was found to encode a 90 kDa integral membrane protein. Some of this protein is cleaved within E. coli to give a soluble N-terminal region that can easily be purified and yields a 50 kDa flavoprotein. When expressed in harness with the genes for precorrin-3a synthesis, ORF663 appears to mediate the transformation of precorrin-3a into a new chromophoric compound. Another open reading frame in close proximity to orf663 is termed orf647, and was found to encode a 2Fe-2S ferredoxin-like protein. We suggest that these two proteins may provide an alternative oxygen-independent mechanism for ring contraction within R. capsulatus.

UI	MeSH Term	Description	Entries
D009876	Operon	In bacteria, a group of metabolically related genes, with a common promoter, whose transcription into a single polycistronic MESSENGER RNA is under the control of an OPERATOR REGION.	Operons
D003545	Cysteine	A thiol-containing non-essential amino acid that is oxidized to form CYSTINE.	Cysteine Hydrochloride,Half-Cystine,L-Cysteine,Zinc Cysteinate,Half Cystine,L Cysteine
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D014805	Vitamin B 12	A cobalt-containing coordination compound produced by intestinal micro-organisms and found also in soil and water. Higher plants do not concentrate vitamin B 12 from the soil and so are a poor source of the substance as compared with animal tissues. INTRINSIC FACTOR is important for the assimilation of vitamin B 12.	Cobalamin,Cyanocobalamin,Cobalamins,Eritron,Vitamin B12,B 12, Vitamin,B12, Vitamin
D016354	Rhodobacter capsulatus	Non-pathogenic ovoid to rod-shaped bacteria that are widely distributed and found in fresh water as well as marine and hypersaline habitats.	Rhodopseudomonas capsulatus,Rhodopseudomonas capsulata
D016366	Open Reading Frames	A sequence of successive nucleotide triplets that are read as CODONS specifying AMINO ACIDS and begin with an INITIATOR CODON and end with a stop codon (CODON, TERMINATOR).	ORFs,Protein Coding Region,Small Open Reading Frame,Small Open Reading Frames,sORF,Unassigned Reading Frame,Unassigned Reading Frames,Unidentified Reading Frame,Coding Region, Protein,Frame, Unidentified Reading,ORF,Open Reading Frame,Protein Coding Regions,Reading Frame, Open,Reading Frame, Unassigned,Reading Frame, Unidentified,Region, Protein Coding,Unidentified Reading Frames

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