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.
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Conference Article|
August 01 2002
Cobalamin (vitamin B12) biosynthesis in Rhodobacter capsulatus
H. McGoldrick;
H. McGoldrick
1
1Queen Mary, University of London, London E 4NS, U.K.
1To whom correspondence should be addressed (e-mail H.M.McGoldrick@qmul.ac.uk)
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E. Deery;
E. Deery
1Queen Mary, University of London, London E 4NS, U.K.
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M. Warren;
M. Warren
1Queen Mary, University of London, London E 4NS, U.K.
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P. Heathcote
P. Heathcote
1Queen Mary, University of London, London E 4NS, U.K.
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Publisher: Portland Press Ltd
Received:
March 17 2002
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2002 Biochemical Society
2002
Biochem Soc Trans (2002) 30 (4): 646–648.
Article history
Received:
March 17 2002
Citation
H. McGoldrick, E. Deery, M. Warren, P. Heathcote; Cobalamin (vitamin B12) biosynthesis in Rhodobacter capsulatus. Biochem Soc Trans 1 August 2002; 30 (4): 646–648. doi: https://doi.org/10.1042/bst0300646
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