Characterization of Yeast sar1 Temperature-Sensitive Mutants, Which Are Defective in Protein Transport from the Endoplasmic Reticulum

Abstract

SAR1 encodes a low molecular weight GTPase that is essential in the early pracess of vesicular transport in the secretory pathway. By random and site-directed mutagenesis of the SAR1 gene, we have obtained three temperature-sensitive mutants, N1321, E112K, and D32G. They all show a defect in transport from the endoplasmic reticulum to the Golgi apparatus, and accumulate endoplasmic reticulum membranes at the restrictive temperature. This is consistent with our previous observations in viuo on a galactose-shutoff mutant as well as the in vitro results, and provides powerful tools for further genetic analyses.

Golgi apparatus, protein secretion, small GTPase, Saccharomyces cereuisiae, vesicular transport