Regulation of a cytosolic and nuclear O-GlcNAc transferase. Role of the tetratricopeptide repeats

Lisa K. Kreppel, Gerald Warren Hart

Research output: Contribution to journalArticlepeer-review

Abstract

The O-GlcNAc transferase (OGT) is a unique nuclear and cytosolic glycosyltransferase that contains multiple tetratricopeptide repeats. We have begun to characterize the mechanisms regulating OGT using a combination of deletion analysis and kinetic studies. Here we show that the p110 subunit of the enzyme forms both homo-and heterotrimers that appear to have different binding affinities for UDP-GlcNAc. The multimerization domain of OGT lies within the tetratricopeptide repeat domain and is not necessary for activity. Kinetic analyses of the full-length trimer and the truncated monomer forms of OGT suggest that both forms function through a random bi-bi kinetic mechanism. Both the monomer and trimer have similar specific activities and similar K(m) values for peptide substrates. However, they differ in their binding affinities for UDP-GlcNAc, indicating that subunit interactions affect enzyme activity. The findings that recombinant OGT has three distinct K(m) values for UDP-GlcNAc and that UDP-GlcNAc concentrations modulates the affinity of OGT for peptides suggest that OGT is exquisitely regulated by the levels of UDP-GlcNAc within the nucleus and cytoplasm.

Original languageEnglish (US)
Pages (from-to)32015-32022
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number45
DOIs
StatePublished - Nov 5 1999

ASJC Scopus subject areas

  • Biochemistry

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