Dataset Information

Destabilization of human glycine N-methyltransferase by H176N mutation.

ABSTRACT: In the presence of moderate (2-4 M) urea concentrations the tetrameric enzyme, glycine N-methyltransferase (GNMT), dissociates into compact monomers. Higher concentrations of urea (7-8 M) promote complete denaturation of the enzyme. We report here that the H176N mutation in this enzyme, found in humans with hypermethioninaemia, significantly decreases stability of the tetramer, although H176 is located far from the intersubunit contact areas. Dissociation of the tetramer to compact monomers and unfolding of compact monomers of the mutant protein were detected by circular dichroism, quenching of fluorescence emission, size-exclusion chromatography, and enzyme activity. The values of apparent free energy of dissociation of tetramer and of unfolding of compact monomers for the H176N mutant (27.7 and 4.2 kcal/mol, respectively) are lower than those of wild-type protein (37.5 and 6.2 kcal/mol). A 2.7 A resolution structure of the mutant protein revealed no significant difference in the conformation of the protein near the mutated residue.

SUBMITTER: Luka Z

PROVIDER: S-EPMC2206963 | biostudies-literature | 2007 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Destabilization of human glycine N-methyltransferase by H176N mutation.

Luka Zigmund Z Pakhomova Svetlana S Luka Yury Y Newcomer Marcia E ME Wagner Conrad C

Protein science : a publication of the Protein Society 20070727 9

In the presence of moderate (2-4 M) urea concentrations the tetrameric enzyme, glycine N-methyltransferase (GNMT), dissociates into compact monomers. Higher concentrations of urea (7-8 M) promote complete denaturation of the enzyme. We report here that the H176N mutation in this enzyme, found in humans with hypermethioninaemia, significantly decreases stability of the tetramer, although H176 is located far from the intersubunit contact areas. Dissociation of the tetramer to compact monomers and ...[more]

PMID: 17660255

Similar Datasets

Project description:Hepatic S-adenosylmethionine (SAMe) is maintained constant by the action of methionine adenosyltransferase I/III (MATI/III), which converts methionine into SAMe and glycine N-methyltransferase (GNMT), which eliminates excess SAMe to avoid aberrant methylation reactions. During liver regeneration after partial hepatectomy (PH) MATI/III activity is inhibited leading to a decrease in SAMe. This injury-related reduction in SAMe promotes hepatocyte proliferation because SAMe inhibits hepatocyte DNA synthesis. In MATI/III-deficient mice, hepatic SAMe is reduced, resulting in uncontrolled hepatocyte growth and impaired liver regeneration. These observations suggest that a reduction in SAMe is crucial for successful liver regeneration. In support of this hypothesis we report that liver regeneration is impaired in GNMT knockout (GNMT-KO) mice. Liver SAMe is 50-fold higher in GNMT-KO mice than in control animals and is maintained constant following PH. Mortality after PH was higher in GNMT-KO mice than in control animals. In GNMT-KO mice, nuclear factor kappaB (NFkappaB), signal transducer and activator of transcription-3 (STAT3), inducible nitric oxide synthase (iNOS), cyclin D1, cyclin A, and poly (ADP-ribose) polymerase were activated at baseline. PH in GNMT-KO mice was followed by the inactivation of STAT3 phosphorylation and iNOS expression. NFkappaB, cyclin D1 and cyclin A were not further activated after PH. The LKB1/AMP-activated protein kinase/endothelial nitric oxide synthase cascade was inhibited, and cytoplasmic HuR translocation was blocked despite preserved induction of DNA synthesis in GNMT-KO after PH. Furthermore, a previously unexpected relationship between AMPK phosphorylation and NFkappaB activation was uncovered.These results indicate that multiple signaling pathways are impaired during the liver regenerative response in GNMT-KO mice, suggesting that GNMT plays a critical role during liver regeneration, promoting hepatocyte viability and normal proliferation.

Dataset Information

Destabilization of human glycine N-methyltransferase by H176N mutation.

Publications

Destabilization of human glycine N-methyltransferase by H176N mutation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets