High impact information on STT3

• As no significant nascent chain photocross-linking to other OST subunits was detected in these fully assembled translocation and integration intermediates, our results strongly indicate that the nascent chain portion of the OST active site is located in STT3 [1].
• A mutation in the STT3 locus affects substrate specificity of the OTase complex in vivo and in vitro [2].
• The essential STT3 protein is approximately 60% identical in amino acid sequence to its human homologue [2].
• The highly conserved membrane protein STT3 is part of the oligosaccharyl transferase complex in the endoplasmic reticulum of eukaryotic cells [3].
• Staurosporine is a specific inhibitor of Pkc1p, and a genetic link had previously been suggested between PKC1 and STT3 [4].

Biological context of STT3

• Staurosporine sensitivity was found to be an allele-specific phenotype restricted to cells harboring mutations in highly conserved residues in the N-terminal domain of the STT3 protein [4].
• The product of the essential gene STT3 is required for OTase activity in vivo, but is not present in highly purified OTase preparations [5].
• The STT3 gene encodes a novel 718-amino-acid protein with significant homology to potential transmembrane proteins of Caenorhabditis elegans and mouse mandibular condyle (about 80% homologous and 60% identical) [6].
• Unlike the STT1/PKC1 gene, STT3 is essential for cell growth irrespective of osmotic support [6].
• STT3, a novel essential gene related to the PKC1/STT1 protein kinase pathway, is involved in protein glycosylation in yeast [6].

Analytical, diagnostic and therapeutic context of STT3

• When translocation intermediates with nascent chains of increasing length were irradiated, nascent chain photocross-linking to translocon components, Sec61alpha and TRAM, was replaced by efficient photocross-linking solely to a protein identified by immunoprecipitation as the STT3 subunit of the OST [1].

References