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Title: Differences in folate-protein interactions result in differing inhibition of native rat liver and recombinant glycine N-methyltransferase by 5-methyltetrahydrofolate

Glycine N-methyltransferase (GNMT) is a key regulatory enzyme in methyl group metabolism. In mammalian liver it reduces S-adenosylmethionine levels by using it to methylate glycine, producing N-methylglycine (sarcosine) and S-adenosylhomocysteine. GNMT is inhibited by binding two molecules of 5-methyltetrahydrofolate (mono- or polyglutamate forms) per tetramer of the active enzyme. Inhibition is sensitive to the status of the N-terminal valine of GNMT and to polyglutamation of the folate inhibitor. It is inhibited by pentaglutamate form more efficiently compared to monoglutamate form. The native rat liver GNMT contains an acetylated N-terminal valine and is inhibited much more efficiently compared to the recombinant protein expressed in E. coli where the N-terminus is not acetylated. In this work we used a protein crystallography approach to evaluate the structural basis for these differences. We show that in the folate-GNMT complexes with the native enzyme, two folate molecules establish three and four hydrogen bonds with the protein. In the folate-recombinant GNMT complex only one hydrogen bond is established. This difference results in more effective inhibition by folate of the native liver GNMT activity compared to the recombinant enzyme.
Authors:
; ; ; ;  [1] ;  [2]
  1. Vanderbilt
  2. (
Publication Date:
OSTI Identifier:
1041336
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochimica et Biophysica Acta. Proteins and Proteomics; Journal Volume: 1824; Journal Issue: (2) ; 02, 2012
Publisher:
Elsevier
Research Org:
Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
Sponsoring Org:
OTHEROTHER U.S. GOVERNMENT
Country of Publication:
United States
Language:
ENGLISH
Subject:
08 HYDROGEN; CRYSTAL STRUCTURE; CRYSTALLOGRAPHY; ENZYMES; GLYCINE; HYDROGEN; LIVER; METABOLISM; PROTEINS; SARCOSINE; VALINE