Woodcock, S.C. and Raux, E. and Levillayer, F. and Thermes, C. and Rambach, A. and Warren, M.J. (1998) Effect of mutations in the transmethylase and dehydrogenase/chelatase domains of sirohaem synthase (CysG) on sirohaem and cobalamin biosynthesis. Biochemical Journal, 330 (1). pp. 121-9. ISSN 0264-6021.
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The Escherichia coli CysG protein (sirohaem synthase) catalyses four separate reactions that are required for the transformation of uroporphyrinogen III into sirohaem, initially two S-adenosyl-l-methionine-dependent transmethylations at positions 2 and 7, mediated through the C-terminal, or CysGA, catalytic domain of the protein, and subsequently a ferrochelation and dehydrogenation, mediated through the N-terminal, or CysGB, catalytic domain of the enzyme. This report describes how the deletion of the NAD+-binding site of CysG, located within the first 35 residues of the N-terminus, is detrimental to the activity of CysGB but does not affect the catalytic activity of CysGA, whereas the mutation of a number of phylogenetically conserved residues within CysGA is detrimental to the transmethylation reaction but does not affect the activity of CysGB. Further studies have shown that CysGB is not essential for cobalamin biosynthesis because the presence of the Salmonella typhimurium CobI operon with either cysGA or the Pseudomonas denitrificans cobA are sufficient for the synthesis of cobyric acid in an E. coli cysG deletion strain. Evidence is also presented to suggest that a gene within the S. typhimurium CobI operon might act as a chelatase that, at low levels of cobalt, is able to aid in the synthesis of sirohaem.
|Uncontrolled keywords:||Amino Acid Sequence Consensus Sequence Escherichia coli/enzymology Genetic Complementation Test Heme/analogs & derivatives/biosynthesis Methyltransferases/genetics/*metabolism Molecular Sequence Data Point Mutation S-Adenosylmethionine/metabolism Salmonella typhimurium/genetics Sequence Alignment Sequence Homology, Amino Acid Vitamin B 12/analogs & derivatives/biosynthesis|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||Martin Warren|
|Date Deposited:||15 Oct 2009 08:30|
|Last Modified:||14 Jan 2010 14:42|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/11078 (The current URI for this page, for reference purposes)|
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