Nonlethal sec71-1 and sec72-1 mutations eliminate proteins associated with the Sec63p-BiP complex from S. cerevisiae.
The sec71-1 and sec72-1 mutations were identified by a genetic assay that monitored membrane protein integration into the endoplasmic reticulum (ER) membrane of the yeast Saccharomyces cerevisiae. The mutations inhibited integration of various chimeric membrane proteins and translocation of a subset of water soluble proteins. In this paper we show that SEC71 encodes the 31.5-kDa transmembrane glycoprotein (p31.5) and SEC72 encodes the 23-kDa protein (p23) of the Sec63p-BiP complex. SEC71 is therefore identical to SEC66 (HSS1), which was previously shown to encode p31.5. DNA sequence analyses reveal that sec71-1 cells contain a nonsense mutation that removes approximately two-thirds of the cytoplasmic C-terminal domain of p31.5. The sec72-1 mutation shifts the reading frame of the gene encoding p23. Unexpectedly, the sec71-1 mutant lacks p31.5 and p23. Neither mutation is lethal, although sec71-1 cells exhibit a growth defect at 37 degrees C. These results show that p31.5 and p23 are important for the trafficking of a subset of proteins to the ER membrane.
Department of Microbiology and Immunology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2363.
H
H
Fang
N
N
Green
D000595:Amino Acid Sequence; D001483:Base Sequence; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C060153:KAR2 protein, yeast; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C074215:SEC63 protein, S cerevisiae; C088668:SEC72 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins