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2e0k

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{{STRUCTURE_2e0k| PDB=2e0k | SCENE= }}
{{STRUCTURE_2e0k| PDB=2e0k | SCENE= }}
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'''Crystal structure of CbiL, a methyltransferase involved in anaerobic vitamin B12 biosynthesis'''
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===Crystal structure of CbiL, a methyltransferase involved in anaerobic vitamin B12 biosynthesis===
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==Overview==
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During anaerobic cobalamin (vitamin B12) biosynthesis, CbiL catalyzes methylation at the C-20 position of a cyclic tetrapyrrole ring using S-adenosylmethionine as a methyl group source. This methylation is a key modification for the ring contraction process, by which a porphyrin-type tetrapyrrole ring is converted to a corrin ring through elimination of the modified C-20 and direct bonding of C-1 to C-19. We have determined the crystal structures of Chlorobium tepidum CbiL and CbiL in complex with S-adenosylhomocysteine (the S-demethyl form of S-adenosylmethionine). CbiL forms a dimer in the crystal, and each subunit consists of N-terminal and C-terminal domains. S-Adenosylhomocysteine binds to a cleft between the two domains, where it is specifically recognized by extensive hydrogen bonding and van der Waals interactions. The orientation of the cobalt-factor II substrate was modeled by simulation, and the predicted model suggests that the hydroxy group of Tyr226 is located in close proximity to the C-20 atom as well as the C-1 and C-19 atoms of the tetrapyrrole ring. These configurations allow us to propose a catalytic mechanism: the conserved Tyr226 residue in CbiL catalyzes the direct transfer of a methyl group from S-adenosylmethionine to the substrate through an S(N)2-like mechanism. Furthermore, the structural model of CbiL binding to its substrate suggests the axial residue coordinated to the central cobalt of cobalt-factor II.
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{{ABSTRACT_PUBMED_17229157}}
==About this Structure==
==About this Structure==
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[[Category: S-adenosylmethionine]]
[[Category: S-adenosylmethionine]]
[[Category: Tetrapyrrole]]
[[Category: Tetrapyrrole]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 15:04:02 2008''

Revision as of 12:04, 28 July 2008

Image:2e0k.png

Template:STRUCTURE 2e0k

Crystal structure of CbiL, a methyltransferase involved in anaerobic vitamin B12 biosynthesis

Template:ABSTRACT PUBMED 17229157

About this Structure

2E0K is a Single protein structure of sequence from Chlorobaculum tepidum. Full crystallographic information is available from OCA.

Reference

Crystal structures of CbiL, a methyltransferase involved in anaerobic vitamin B biosynthesis, and CbiL in complex with S-adenosylhomocysteine--implications for the reaction mechanism., Wada K, Harada J, Yaeda Y, Tamiaki H, Oh-Oka H, Fukuyama K, FEBS J. 2007 Jan;274(2):563-73. PMID:17229157

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