Using x-ray crystallography, researchers have produced the first images of a large molecular complex that helps shape and load the small, bubble-like vesicles that transport newly formed proteins in the cell. Understanding vesicle "budding" is one of the prerequisites for learning how proteins and other molecules are routed to their correct destinations in the cell.

In an article published in the September 19, 2002, issue of the journal Nature, Howard Hughes Medical Institute (HHMI) investigator Jonathan Goldberg, Xiping Bi and Richard Corpina at Memorial Sloan-Kettering Cancer Center unveil the intricate architecture of the "pre-budding complex," which is a set of proteins that participates in the formation of vesicles on the cell's endoplasmic reticulum (ER). The pre-budding complex is the triggering component of a protein coat called COPII that grabs a section of the ER membrane, pinches it off to form the vesicle and packages the protein cargo to be transported.

"The structure developed by Bi, Corpina and Goldberg makes an important contribution to the understanding of vesicle formation -- a process central to the transport of newly formed proteins," said HHMI investigator Randy Schekman, a pioneer in vesicle studies at the University of California, Berkeley. "It illuminates in detail the mechanism by which the core complex of the COPII protein coat assembles on the ER membrane to initiate the process of membrane cargo capture and vesicle budding." Schekman and James Rothman of Memorial Sloan-Kettering Cancer Center, working independently, have identified many of the fundamental details of protein transport and secretion.

Goldberg said the entire pre-budding complex was considered an important structure to solve because of COPII's role in protein transport. "What makes the COPII coat unique is
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
18-Sep-2002

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