J Biol Chem, Vol. 274, Issue 16, 11296-11302, April 16, 1999
Disruption of YHC8, a Member of the TSR1
Gene Family, Reveals Its Direct Involvement in Yeast Protein
Translocation
Choukri Ben
Mamoun
§,
Jean-Marie
Beckerich
,
Claude
Gaillardin
, and
Francois
Kepes
From the
Laboratoire de Génétique
Moléculaire et Cellulaire, INRA-CNRS, Centre de Biotechnologie
Agro Industrielle, Institut National Agronomique Paris-Grignon,
78850 Thiverval-Grignon, France, § Departments of
Molecular Microbiology and Medicine, Washington University School of
Medicine, St. Louis, Missouri 63110,
Service de Biochimie et
de Génétique Moléculaire, DBCM/DSV, BAT.142,
CEA/Saclay, 91191 Gif Cedex, France
Genetic studies of Saccharomyces
cerevisiae have identified many components acting to deliver
specific proteins to their cellular locations. Genome analysis,
however, has indicated that additional genes may also participate in
such protein trafficking. The product of the yeast Yarrowia
lipolytica TSR1 gene promotes the signal recognition
particle-dependent translocation of secretory proteins through the endoplasmic reticulum. Here we describe the identification of a new gene family of proteins that is well conserved among different
yeast species. The TSR1 genes encode polypeptides that share the same protein domain distribution and, like Tsr1p, may play an
important role in the early steps of the signal recognition particle-dependent translocation pathway. We have
identified five homologues of the TSR1 gene, four of them
from the yeast Saccharomyces cerevisiae and the other from
Hansenula polymorpha. We generated a null mutation in the
S. cerevisiae YHC8 gene, the closest homologue to Y. lipolytica TSR1, and used different soluble (carboxypeptidase Y,
-factor, invertase) and membrane (dipeptidyl-aminopeptidase) secretory proteins to study its phenotype. A large accumulation of
soluble protein precursors was detected in the mutant strain. Immunofluorescence experiments show that Yhc8p is localized in the
endoplasmic reticulum. We propose that the YHC8 gene is a new and important component of the S. cerevisiae
endoplasmic reticulum membrane and that it functions in protein
translocation/insertion of secretory proteins through or into this compartment.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.