By Randy Schekman (HHMI/University of California, Berkeley)
In this talk, Randy Schekman describes a genetic screen in yeast and then follow-up studies in vitro (in the test tube).
- Why would a scientist reconstruct vesicle budding in vitro when this phenomenon can be readily observed in live cells?
- What are some of the advantages of using biochemical techniques to study the secretory pathway?
Studying Protein Secretion in Yeast
|Length: 36:35 minDownload: This Video|
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Biochemical Reconstitution of Transport Vesicle Budding
|Length: 25:15 minDownload: This Video|
Protein secretion is executed by a cellular pathway involving the delivery of membrane and soluble secretory proteins in vesicles that capture newly-synthesized proteins assembled in the endoplasmic reticulum (ER) and sorted in the Golgi apparatus. Vesicles fuse with the plasma membrane resulting in the discharge of soluble molecules to the cell exterior and integration of vesicle membrane proteins and lipids in the cell surface. Baker’s yeast cells grow by vesicle fusion and secretion at the tip of the daughter bud. A genetic dissection of this process was performed with temperature sensitive conditional mutants blocked at one of several stations in the secretory pathway.
Secretion mutants that block protein exit from the endoplasmic reticulum define genes involved in the formation, targeting and fusion of a small vesicle intermediate. SEC genes corresponding to the mutants defective in vesicle budding define the cytoplasmic machinery responsible for transport vesicle morphogenesis. A biochemical reaction that reproduces ER vesicle budding was reconstituted with gently-broken yeast cells and pure recombinant Sec proteins required in vivo for this budding event. The Sec proteins assemble on the ER membrane in the presence of GTP which activates a small GTPase, Sar1, initiating the formation of a coat protein complex called COPII.
Dr. Randy Schekman is a Professor in the Department of Molecular and Cell Biology, University of California, Berkeley, and an Investigator of the Howard Hughes Medical Institute. He studied the enzymology of DNA replication as a graduate student with Arthur Kornberg at Stanford University. His current interest in cellular membranes developed during a postdoctoral period with S. J. Singer at the University of California, San Diego. At Berkeley, he developed a genetic and biochemical approach to the study of eukaryotic membrane traffic.
Among his awards are the Eli Lilly Award in microbiology and immunology, the Lewis S. Rosenstiel Award in basic biomedical science, the Gairdner International Award, the Amgen Award of the Protein Society, the Albert Lasker Award in Basic Medical Research and the Louisa Gross Horwitz Prize of Columbia University. In 2013, Schekman was awarded the Nobel Prize in Medicine or Physiology jointly with Thomas Südhof and James Rothman for their contributions to understanding vesicle trafficking.
Schekman has been awarded honorary doctorate degrees from the University of Geneva and the University of Regensburg. He is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. From 2006-2011, he was Editor-in-Chief of the Proceeding of the NAS. Currently he is Editor-in-Chief of the open access journal eLife.
- Randy Schekman iBioSeminar Part 3: Human Diseases of Vesicle Budding
- Randy Schekman iBioEducation Lecture: Mysterious Membranes
- Peter Walter iBioMagazine: Unfolding the UPR