title: Functional Similarities between the Protein O-Mannosyltransferases Pmt4 from Bakers' Yeast and Human POMT1.
abstract: Protein O-mannosylation is an essential post-translational modification. It is initiated in the endoplasmic reticulum by a family of protein O-mannosyltransferases that are conserved from yeast (PMTs) to human (POMTs). The degree of functional conservation between yeast and human protein O-mannosyltransferases is uncharacterized. In bakers' yeast, the main in vivo activities are due to heteromeric Pmt1-Pmt2 and homomeric Pmt4 complexes. Here we describe an enzymatic assay that allowed us to monitor Pmt4 activity in vitro We demonstrate that detergent requirements and acceptor substrates of yeast Pmt4 are different from Pmt1-Pmt2, but resemble that of human POMTs. Furthermore, we mimicked two POMT1 amino acid exchanges (G76R and V428D) that result in severe congenital muscular dystrophies in humans, in yeast Pmt4 (I112R and I435D). In vivo and in vitro analyses showed that general features such as protein stability of the Pmt4 variants were not significantly affected, however, the mutants proved largely enzymatically inactive. Our results demonstrate functional and biochemical similarities between POMT1 and its orthologue from bakers' yeast Pmt4.
authors.affiliation: From the Centre for Organismal Studies, Cell Chemistry, Heidelberg University, 69120 Heidelberg, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bausewein
authors.affiliation: From the Centre for Organismal Studies, Cell Chemistry, Heidelberg University, 69120 Heidelberg, Germany.
authors.forename: Jakob
authors.initials: J
authors.lastname: Engel
authors.affiliation: From the Centre for Organismal Studies, Cell Chemistry, Heidelberg University, 69120 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jank
authors.affiliation: From the Centre for Organismal Studies, Cell Chemistry, Heidelberg University, 69120 Heidelberg, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Schoedl
authors.affiliation: From the Centre for Organismal Studies, Cell Chemistry, Heidelberg University, 69120 Heidelberg, Germany sabine.strahl@cos.uni-heidelberg.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Strahl
mesh_terms: D019943:Amino Acid Substitution; D004795:Enzyme Stability; D006801:Humans; D008364:Mannosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D008364:Mannosyltransferases; C082696:protein O-mannosyltransferase
keywords: O-mannosylation; PMT4; POMT1; dystroglycanopathy; enzyme mutation; glycosylation; glycosyltransferase; human; yeast