Hl. Schubert et al., THE X-RAY STRUCTURE OF A COBALAMIN BIOSYNTHETIC ENZYME, COBALT-PRECORRIN-4 METHYLTRANSFERASE, Nature structural biology, 5(7), 1998, pp. 585-592
Biosynthesis of the corrin ring of vitamin B-12 requires the action of
six S-adenosyl-L-methionine (AdoMet) dependent transmethylases, close
ly related in sequence. The first X-ray structure of one of these, cob
alt-precorrin-4 transmethylase, CbiF, from Bacillus megaterium has bee
n determined to a resolution of 2.4 Angstrom. CbiF contains two alpha/
beta domains forming a trough in which S-adenosyl-L-homocysteine (AdoH
cy) binds. The location of AdoHcy and a number of conserved residues,
helps define the precorrin binding site. A second crystal form determi
ned at 3.1 Angstrom resolution highlights the flexibility of two loops
around this site. CbiF employs a unique mode of AdoHcy binding and re
presents a new class of transmethylase.