Multiple SecA molecules drive protein translocation across a single translocon with SecG inversion |
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Authors: | Morita Kazuhiro Tokuda Hajime Nishiyama Ken-ichi |
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Institution: | Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan. |
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Abstract: | SecA is a translocation ATPase that drives protein translocation. D209N SecA, a dominant-negative mutant, binds ATP but is unable to hydrolyze it. This mutant was inactive to proOmpA translocation. However, it generated a translocation intermediate of 18 kDa. Further addition of wild-type SecA caused its translocation into either mature OmpA or another intermediate of 28 kDa that can be translocated into mature by a proton motive force. The addition of excess D209N SecA during translocation caused a topology inversion of SecG. Moreover, an intermediate of SecG inversion was identified when wild-type and D209N SecA were used in the same amounts. These results indicate that multiple SecA molecules drive translocation across a single translocon with SecG inversion. Here, we propose a revised model of proOmpA translocation in which a single catalytic cycle of SecA causes translocation of 10-13 kDa with ATP binding and hydrolysis, and SecG inversion is required when the next SecA cycle begins with additional ATP hydrolysis. |
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Keywords: | ATPases Protein Export Protein Secretion Protein Translocation Transport SecA SecYEG Topology Inversion of SecG Translocon |
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