BY SIMON SILVER
Department of Microbiology & Immunology
University of Illinois
The protein secretory apparatus E. coli is being taken apart and put together in vitro like a Tinkertoy: SecA is a peripheral membrant ATPase of 102 kdaltons. SecB is separate and exists as a cytoplasmic tetramer of 16x4=64 kdaltons that is sufficient by itself for transport of some exported polypeptides.
M. Watanabe, G. Blobel, “Cytosolic factor purified from Escherichia coli is necessary and sufficient for the export of a preprotein and is a homotetramer of SecB,” Proceedings of the National Academy of Sciences, USA, 86,2728-32, April 1989. (The Rockefeller University, New York, N.Y.)
K. Cunningham, R. Lill, E. Crooke, M. Rice, et al., “SecA protein, a peripheral protein of the Escherichia coli plasma membrane, is essential for the functional binding and translocation of proOmpA,” EMBO Journal, 8. 955-9, March 1989. (University...