title: The transitional ER localization mechanism of Pichia pastoris Sec12.
abstract: COPII vesicles assemble at ER subdomains called transitional ER (tER) sites, but the mechanism that generates tER sites is unknown. To study tER biogenesis, we analyzed the transmembrane protein Sec12, which initiates COPII vesicle formation. Sec12 is concentrated at discrete tER sites in the budding yeast Pichia pastoris. We find that P. pastoris Sec12 exchanges rapidly between tER sites and the general ER. The tER localization of Sec12 is saturable and is mediated by interaction of the Sec12 cytosolic domain with a partner component. This interaction apparently requires oligomerization of the Sec12 lumenal domain. Redistribution of P. pastoris Sec12 to the general ER does not perturb the localization of downstream tER components, suggesting that Sec12 and other COPII proteins associate with a tER scaffold. These results provide evidence that tER sites form by a network of dynamic associations at the cytosolic face of the ER.
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
authors.forename: Jon
authors.initials: J
authors.lastname: Soderholm
authors.forename: Dibyendu
authors.initials: D
authors.lastname: Bhattacharyya
authors.forename: Daniel
authors.initials: D
authors.lastname: Strongin
authors.forename: Vida
authors.initials: V
authors.lastname: Markovitz
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Connerly
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Reinke
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Glick
mesh_terms: D022181:COP-Coated Vesicles / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D020662:Guanine Nucleotide Exchange Factors; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D010843:Pichia / Q000378:metabolism* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C071239:SEC12 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins