PMID: 9655336

Authors:

Pattanayek R, Newcomer ME, Wagner C

Title:

Crystal structure of apo-glycine N-methyltransferase (GNMT).

Journal:

Protein Sci. 1998 Jun;7(6):1326-31.

Abstract:

The crystal structure of the recombinant apo-form of glycine N-methyltransferase (GNMT) has been determined at 2.5 A resolution. GNMT is a tetrameric enzyme (monomer Mr = 32,423Da, 292 amino acids) that catalyzes the transfer of a methyl group from S-adenosylmethionine (AdoMet) to glycine with the formation of S-adenosylhomocysteine (AdoHcy) and sarcosine (N-methylglycine). GNMT is a regulatory enzyme, which is inhibited by 5-methyltetrahydrofolate pentaglutamate and believed to control the ratio of AdoMet to AdoHcy in tissues. The crystals belong to the orthorhombic space group P2(1)2(1)2 (a = 85.39, b = 174.21, c = 44.71 A) and contain one dimer per asymmetric unit. The AdoMet-GNMT structure served as the starting model. The structure was refined to an R-factor of 21.9%. Each monomer is a three-domain structure with a large cavity enclosed by the three domains. The tetramer resembles a square with a central channel about which N-terminal domains are intertwined. Only localized changes of the residues involved in the binding pocket are observed for the apo-GNMT structure when compared to that determined in the presence of substrate and substrate analog.