High impact information on SEC16

• SEC16 encodes a 240-kD hydrophilic protein that is required for transport vesicle budding from the ER in Saccharomyces cerevisiae [1].
• We propose that Sec16p nucleates a Sar1-GTP-dependent initiation of COPII assembly and serves to stabilize the coat to premature disassembly after Sar1p hydrolyzes GTP [1].
• Sec16p is tightly and peripherally bound to ER membranes, hence it is not one of the cytosolic proteins required to reconstitute transport vesicle budding in a cell-free reaction [1].
• Although COPII vesicle budding is promoted by GTP or a nonhydrolyzable analogue, guanylimide diphosphate (GMP-PNP), Sec16p stimulation is dependent on GTP in the reaction [1].
• Details of coat protein assembly and Sec16p-stimulated vesicle budding were explored with synthetic liposomes composed of a mixture of lipids, including acidic phospholipids (major-minor mix), or a simple binary mixture of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) [1].

Biological context of SEC16

• Three other coatmer protein (COPII) mutants, sec16, sec23, and sec24, were also defective in autophagy [2].

Anatomical context of SEC16

• SEC16 is required for transport vesicle budding from the ER in Saccharomyces cerevisiae, and encodes a large hydrophilic protein found on the ER membrane and as part of the coat of transport vesicles [3].
• SED4 encodes a yeast endoplasmic reticulum protein that binds Sec16p and participates in vesicle formation [3].
• Finally, we show that membranes prepared from strains with mutations in the SEC16 gene are more defective for the packaging of v-SNARE molecules and Emp24p than they are for the packaging of gp alphaF [4].

Associations of SEC16 with chemical compounds

• Sec16p is released from this particulate fraction by high salt, but not by nonionic detergents or urea [5].

Physical interactions of SEC16

• Yeast SEC16 gene encodes a multidomain vesicle coat protein that interacts with Sec23p [5].
• Second, we show that a truncation mutant of Sec31p specifically defective for Sec16p binding is unable to complement a sec31Delta mutant and cannot rescue the secretion defect of a temperature-sensitive sec31 mutant at nonpermissive temperatures [6].
• Here we use two-hybrid and coprecipitation assays to demonstrate that the essential COPII protein Sec24p binds to the central region of Sec16p [7].

Regulatory relationships of SEC16

• Sec16p binds to major-minor mix liposomes and facilitates the recruitment of COPII proteins and vesicle budding in a reaction that is stimulated by Sar1p and GMP-PNP [1].

Other interactions of SEC16

• In a screen to find functionally related genes, we isolated SED4 as a dosage-dependent suppressor of temperature-sensitive SEC16 mutations [3].
• In the delta(sed4) background, the suppression activity of SAR1 towards sec12 and sec16 is lost [8].
• First, we map onto Sec31p binding regions for Sec16p, Sec23p, Sec24p, and Sec13p [6].
• They also suppressed yeast sec12 and sec16 temperature-sensitive mutations as yeast SAR1 does [9].
• These findings indicate that Sec16p associates with Sec23p as part of the transport vesicle coat structure [5].

Analytical, diagnostic and therapeutic context of SEC16

• Sed4p is an integral ER membrane protein whose cytosolic domain binds to the COOH-terminal domain of Sec16p as shown by two-hybrid assay and coprecipitation [3].
• Some Sec16p is localized to the ER by immunofluorescence microscopy [5].
• Thin-section electron microscopy confirms a stimulation of budding profiles produced by incubation of liposomes with COPII and Sec16p [1].

References