A large conformational change of the translocation ATPase SecA
The ATPase SecA mediates the posttranslational translocation of a wide range of polypeptide substrates through the SecY channel in the cytoplasmic membrane of bacteria. We have determined the crystal structure of a monomeric form of Bacillus subtilis SecA at a 2.2-Å resolution. A comparison with the previously determined structures of SecA reveals a nucleotide-independent, large conformational change that opens a deep groove similar to that in other proteins that interact with diverse polypeptides. We propose that the open form of SecA represents an activated state.
© 2004 National Academy of Sciences. Edited by Arthur Horwich, Yale University School of Medicine, New Haven, CT, and approved June 10, 2004 (received for review March 11, 2004). We thank S. Harrison for advice and critical reading of the manuscript; T. Ellenberger for discussions; B. van den Berg, U. Unligil, E. Toth, D. King, T. Hollis, and M. Groll for advice and reagents; M. Becker, L. Berman, and S. LaMarra for support at beamline X25 (Brookhaven National Laboratory, supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences, under contract no. DE-AC02-98CH10886); and A. Joachimiak, S. Ginell, and R. Alkire at beamline ID19 (Advanced Photon Source, supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. W-31-109-ENG-38). We also thank Y. Modis and E. Or for critical reading of the manuscript. The work was supported by a grant from the National Institutes of Health (to T.A.R.). T.A.R. is a Howard Hughes Medical Institute Investigator. W.M.C. was supported by a fellowship from the Damon Runyon Cancer Research Foundation. This paper was submitted directly (Track II) to the PNAS office. Abbreviations: NBF1/2, nucleotide-binding folds 1 and 2; PPXD, preprotein crosslinking domain; HSD, helical scaffold domain; HWD, helical wing domain. Data deposition: The atomic coordinates have been deposited in the Protein Data Bank, www.pdb.org (PDB ID codes 1TF5 and 1TF2 for the nucleotide-free and ADP-bound forms of SecA, respectively).
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