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Molecular recognition in the binding of vitamin B 12 by the cobalamin‐specific Intrinsic Factor
Author(s) -
Andrews Elizabeth R.,
Pratt John M.,
Brown Kenneth L.
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)80365-a
Subject(s) - cobalamin , corrinoid , intrinsic factor , chemistry , stereochemistry , vitamin b12 , cyanocobalamin , side chain , corrin , binding site , biochemistry , crystallography , organic chemistry , methyltransferase , methylation , gene , polymer
Equilibrium constants (given as log K/M −1 ) have been determined at pH 7.4 and 4*C for binding by porcine Intrinsic Factor (B 12 ‐binding protein from the gut, specific for the ‘cobalamin’ series of Co corrinoids) of vitamin B 12 or cyanocobalamin (10.5), cyanocobinamide, α‐ribazole and α‐ribazole‐phosphate (main fragments produced by cleaving off the ‘cobalamin’ side‐chain, all ≤ 3), and cyanocobinamide in the presence of ≥ 10 −9 M ribazole (5.6 and independent of ribazole concentration), i.e. ribazole catalyses the binding of the cobinamide. It is proposed that the specificity of Intrinsic Factor for the cobalamins depends on the presence of the ribazole fragment in the cobalamin side‐chain to promote an essential change in conformation before the corrinoid fragments can be bound.