Publication Date:
1994-12-09
Description:
The crystal structure of a 27-kilodalton methylcobalamin-containing fragment of methionine synthase from Escherichia coli was determined at 3.0 A resolution. This structure depicts cobalamin-protein interactions and reveals that the corrin macrocycle lies between a helical amino-terminal domain and an alpha/beta carboxyl-terminal domain that is a variant of the Rossmann fold. Methylcobalamin undergoes a conformational change on binding the protein; the dimethylbenzimidazole group, which is coordinated to the cobalt in the free cofactor, moves away from the corrin and is replaced by a histidine contributed by the protein. The sequence Asp-X-His-X-X-Gly, which contains this histidine ligand, is conserved in the adenosylcobalamin-dependent enzymes methylmalonyl-coenzyme A mutase and glutamate mutase, suggesting that displacement of the dimethylbenzimidazole will be a feature common to many cobalamin-binding proteins. Thus the cobalt ligand, His759, and the neighboring residues Asp757 and Ser810, may form a catalytic quartet, Co-His-Asp-Ser, that modulates the reactivity of the B12 prosthetic group in methionine synthase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Drennan, C L -- Huang, S -- Drummond, J T -- Matthews, R G -- Lidwig, M L -- GM08570/GM/NIGMS NIH HHS/ -- GM16429/GM/NIGMS NIH HHS/ -- GM24908/GM/NIGMS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1994 Dec 9;266(5191):1669-74.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biophysics Research Division, University of Michigan, Ann Arbor 48109-1055.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7992050" target="_blank"〉PubMed〈/a〉
Keywords:
5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase/*chemistry/metabolism
;
Amino Acid Isomerases/chemistry
;
Amino Acid Sequence
;
Benzimidazoles
;
Catalysis
;
Computer Graphics
;
Crystallography, X-Ray
;
Electron Spin Resonance Spectroscopy
;
Escherichia coli/*enzymology
;
Histidine/metabolism
;
*Intramolecular Transferases
;
Ligands
;
Methylation
;
Methylmalonyl-CoA Mutase/chemistry
;
Models, Molecular
;
Molecular Sequence Data
;
Protein Conformation
;
Protein Folding
;
Protein Structure, Secondary
;
Vitamin B 12/*analogs & derivatives/chemistry/metabolism
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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