title: Molecular dissection of Erv26p identifies separable cargo binding and coat protein sorting activities.
abstract: Efficient export of secretory alkaline phosphatase (ALP) from the endoplasmic reticulum depends on the conserved transmembrane sorting adaptor Erv26p/Svp26p. In the present study we investigated the mechanism by which Erv26p couples pro-ALP to the coat protein complex II (COPII) export machinery. Site-specific mutations were introduced into Erv26p, and mutant proteins were assessed in cell-free assays that monitor interactions with pro-ALP cargo and packaging into COPII vesicles. Mutations in the second and third loop domains of Erv26p inhibited interaction with pro-ALP, whereas mutations in the C-terminal tail sequence influenced incorporation into COPII vesicles and subcellular distribution. Interestingly mutations in the second loop domain also influenced Erv26p homodimer associations. Finally we demonstrated that Ktr3p, a cis-Golgi-localized mannosyltransferase, also relies on Erv26p for efficient COPII-dependent export from the endoplasmic reticulum. These findings demonstrate that Erv26p acts as a protein sorting adaptor for a variety of Type II transmembrane cargo proteins and requires domain-specific interactions with both cargo and coat subunits to promote efficient secretory protein transport.
authors: Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
authors: Catherine A
authors: CA
authors: Bue
authors: Charles
authors: C
authors: Barlowe
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D022181:COP-Coated Vesicles / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C503875:SVP26 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D008364:Mannosyltransferases; D000469:Alkaline Phosphatase