Mutation of the homologue of GDP-mannose pyrophosphorylase alters cell wall structure, protein glycosylation and secretion in Hansenula polymorpha

A Hansenula polymorpha mutant with enhanced ability to secrete a heterologous protein has been isolated. The mutation defines a gene, designated OPU24, which encodes a protein highly homologous to GDP-mannose pyrophosphorylase Psa1p/Srb1p/Vig9p of Saccharomyces cerevisiae and CaSrb1p of Candida albicans. The opu24 mutant manifests phenotypes similar to those of S, cerevisiae mutants depleted for GDP-mannose, such as cell wall fragility and defects in N- and O-glycosylation of secreted proteins. The influence of the opu24 mutation on endoplasmic reticulum-associated protein degradation is discussed. The GenBank Accession No. for the OPU24 sequence is AF234177, Copy-right (C) 2001 John Wiley & Sons, Ltd.