Recognition of a subset of signal sequences by Ssh1p, a Sec61p-related protein in the membrane of endoplasmic reticulum of yeast Saccharomyces cerevisiae.
Ssh1p of Saccharomyces cerevisiae is related in sequence to Sec61p, a general receptor for signal sequences and the major subunit of the channel that guides proteins across the membrane of the endoplasmic reticulum. The split-ubiquitin technique was used to determine whether Ssh1p serves as an additional receptor for signal sequences in vivo. We measured the interactions between the N(ub)-labeled Ssh1p and C(ub)-translocation substrates bearing four different signal sequences. The so-determined interaction profile of Ssh1p was compared with the signal sequence interaction profile of the correspondingly modified N(ub)-Sec61p. The assay reveals interactions of Ssh1p with the signal sequences of Kar2p and invertase, whereas Sec61p additionally interacts with the signal sequences of Mfalpha1 and carboxypeptidase Y. The measured physical proximity between Ssh1p and the beta-subunit of the signal sequence recognition particle receptor confirms our hypothesis that Ssh1p is directly involved in the cotranslational translocation of proteins across the membrane of the endoplasmic reticulum.
Max-Delbrück-Laboratorium, 50829 Cologne, Germany.
Sandra
S
Wittke
Martin
M
Dünnwald
Markus
M
Albertsen
Nils
N
Johnsson
D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D016366:Open Reading Frames; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D018000:Receptors, Peptide / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin / Q000378:metabolism; D043324:beta-Fructofuranosidase
D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; C060153:KAR2 protein, yeast; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C036318:signal peptide receptor; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase