Sfb2p, a yeast protein related to Sec24p, can function as a constituent of COPII coats required for vesicle budding from the endoplasmic reticulum.
The COPII coat is required for vesicle budding from the endoplasmic reticulum (ER), and consists of two heterodimeric subcomplexes, Sec23p/Sec24p, Sec13p/Sec31p, and a small GTPase, Sar1p. We characterized a yeast mutant, anu1 (abnormal nuclear morphology) exhibiting proliferated ER as well as abnormal nuclear morphology at the restrictive temperature. Based on the finding that ANU1 is identical to SEC24, we confirmed a temperature-sensitive protein transport from the ER to the Golgi in anu1-1/sec24-20 cells. Overexpression of SFB2, a SEC24 homologue with 56% identity, partially suppressed not only the mutant phenotype of sec24-20 cells but also rescued the SEC24-disrupted cells. Moreover, the yeast two-hybrid assay revealed that Sfb2p, similarly to Sec24p, interacted with Sec23p. In SEC24-disrupted cells rescued by overexpression of SFB2, some cargo proteins were still retained in the ER, while most of the protein transport was restored. Together, these findings strongly suggest that Sfb2p functions as the component of COPII coats in place of Sec24p, and raise the possibility that each member of the SEC24 family of proteins participates directly and/or indirectly in cargo-recognition events with its own cargo specificity at forming ER-derived vesicles.
Higashio
H
H
Research and Education Center for Genetic Information, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan.
Kimata
Y
Y
Kiriyama
T
T
Hirata
A
A
Kohno
K
K
D022181:COP-Coated Vesicles; D019281:Dimerization; D004721:Endoplasmic Reticulum / Q000502:physiology* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D015966:Gene Expression Regulation, Fungal; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins; D012441:Saccharomyces cerevisiae / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D028861:Nuclear Pore Complex Proteins; C079620:SEC13 protein, S cerevisiae; C079037:SEC23 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; C492204:SFB2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D020559:Monomeric GTP-Binding Proteins; C077395:SAR1 protein, S cerevisiae