A large conformational change of the translocation ATPase SecA.

Andrew R Osborne, William M Clemons, Tom A Rapoport

Index: Proc. Natl. Acad. Sci. U. S. A. 101(30) , 10937-10942, (2004)

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Abstract

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-A 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.