Protein translocation mutants defective in the insertion of integral membrane proteins into the endoplasmic reticulum.
AUTOR(ES)
Stirling, C J
RESUMO
Yeast mutants defective in the translocation of soluble secretory proteins into the lumen of the endoplasmic reticulum (sec61, sec62, sec63) are not impaired in the assembly and glycosylation of the type II membrane protein dipeptidylaminopeptidase B (DPAPB) or of a chimeric membrane protein consisting of the multiple membrane-spanning domain of yeast hydroxymethylglutaryl CoA reductase (HMG1) fused to yeast histidinol dehydrogenase (HIS4C). This chimera is assembled in wild-type or mutant cells such that the His4c protein is oriented to the ER lumen and thus is not available for conversion of cytosolic histidinol to histidine. Cells harboring the chimera have been used to select new translocation defective sec mutants. Temperature-sensitive lethal mutations defining two complementation groups have been isolated: a new allele of sec61 and a single isolate of a new gene sec65. The new isolates are defective in the assembly of DPAPB, as well as the secretory protein alpha-factor precursor. Thus, the chimeric membrane protein allows the selection of more restrictive sec mutations rather than defining genes that are required only for membrane protein assembly. The SEC61 gene was cloned, sequenced, and used to raise polyclonal antiserum that detected the Sec61 protein. The gene encodes a 53-kDa protein with five to eight potential membrane-spanning domains, and Sec61p antiserum detects an integral protein localized to the endoplasmic reticulum membrane. Sec61p appears to play a crucial role in the insertion of secretory and membrane polypeptides into the endoplasmic reticulum.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=275513Documentos Relacionados
- An ATP transporter is required for protein translocation into the yeast endoplasmic reticulum.
- Translocation of rubella virus glycoprotein E1 into the endoplasmic reticulum.
- Purification of a membrane-associated protein complex required for protein translocation across the endoplasmic reticulum.
- Evidence for the loop model of signal-sequence insertion into the endoplasmic reticulum.
- Association of poliovirus proteins with the endoplasmic reticulum.