[대학원 생명과학과 세미나 안내]
연사 : 하준용 박사(Princeton University)
연제 : The Conserve Oligomeric Golgi Complex: A Dynamic Multisubunit Machine in intracellular trafficking
일시 : 2016년 11월 14일 (월) 오전 11시
장소 : 하나과학관 A동 207호
초청교수 : 송현규 교수
Abstract
Within eukaryotic cells, vesicles ferry cargo from one organelle to another. Faithful cargo delivery requires that the vesicle dock at the correct target membrane. Upon docking, SNARE proteins embedded in the vesicle and target membranes assemble to form complexes capable of catalyzing membrane fusion. Vesicle docking and fusion in vivo requires, in addition to SNAREs, large protein machines called multi-subunit tethering complexes (MTCs). These complexes play roles in vesicle capture and fusion, likely serving both to tether the two membranes together and as chaperones to provide a protected pathway for SNARE assembly. One of the best-studied of these MTCs, the COG (conserved oligomeric Golgi) complex, orchestrates the docking and fusion of vesicles delivering cargo to the Golgi apparatus. As a foundation for understanding how COG (and other, related MTCs) functions, we have been studying its structure using a combination of electron microscopy, NMR, and x-ray crystallography. We have been able to use EM to elucidate the molecular architectures of two four-subunit subassemblies, Cog1-4 and Cog5-8. Most recently, I have finally succeeded in reconstituting the full COG complex, Cog1-8, from bacterially co-expressed subunits. Single-particle EM of negatively stained specimens, combined with extensive class averaging, reveal a remarkably dynamic complex well-suited for the tethering and fusion of membranes. To date, we have determined x-ray or NMR structures for two out of the eight COG subunits (Cog1-8) and have begun to elucidate the intersubunit interactions that stabilize the complex. I determined the first high-resolution structure of a COG subcomplex, formed between the Cog5 and Cog7 subunits. Our structure has been used to design mutations that disrupt the Cog5–Cog7 in vitro and in vivo. I will discuss the impact of these mutations on the stability, localization, and function of the COG complex in human cells.