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EMBO J ; 31(4): 1014-27, 2012 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-22157747

RESUMO

Vesicle budding from the endoplasmic reticulum (ER) employs a cycle of GTP binding and hydrolysis to regulate assembly of the COPII coat. We have identified a novel mutation (sec24-m11) in the cargo-binding subunit, Sec24p, that specifically impacts the GTP-dependent generation of vesicles in vitro. Using a high-throughput approach, we defined genetic interactions between sec24-m11 and a variety of trafficking components of the early secretory pathway, including the candidate COPII regulators, Sed4p and Sec16p. We defined a fragment of Sec16p that markedly inhibits the Sec23p- and Sec31p-stimulated GTPase activity of Sar1p, and demonstrated that the Sec24p-m11 mutation diminished this inhibitory activity, likely by perturbing the interaction of Sec24p with Sec16p. The consequence of the heightened GTPase activity when Sec24p-m11 is present is the generation of smaller vesicles, leading to accumulation of ER membranes and more stable ER exit sites. We propose that association of Sec24p with Sec16p creates a novel regulatory complex that retards the GTPase activity of the COPII coat to prevent premature vesicle scission, pointing to a fundamental role for GTP hydrolysis in vesicle release rather than in coat assembly/disassembly.


Assuntos
Vesículas Revestidas pelo Complexo de Proteína do Envoltório/fisiologia , Guanosina Trifosfato/metabolismo , Guanosina Trifosfato/fisiologia , Proteínas de Membrana/fisiologia , Proteínas de Saccharomyces cerevisiae/fisiologia , Proteínas de Membrana/química , Microscopia Eletrônica , Microscopia de Fluorescência , Modelos Moleculares , Proteínas de Saccharomyces cerevisiae/química , Técnicas do Sistema de Duplo-Híbrido
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