SecM facilitates translocase function of SecA by localizing its biosynthesis.
"Arrest sequence" of Escherichia coli SecM interacts with the ribosomal exit tunnel and arrests its own translation elongation, which is released by cotranslational export of the nascent SecM chain. This property of SecM is essential for the basal and regulated expression of SecA. Here we report that SecM has an additional role of facilitating SecA activities. Systematic determinations of the SecA-abundance-protein export relationships of cells with different SecA contents revealed that SecA was less functional when SecM was absent from the upstream region of the secM-secA message, when SecM had the arrest-defective mutation, and also when SecM lacked the signal sequence. These results suggest that cotranslational targeting of nascent SecM to the translocon plays previously unrecognized roles of facilitating the formation of functional SecA molecules. Biosynthesis in the vicinity of the membrane and the Sec translocon will be beneficial for this multiconformation ATPase to adopt ready-to-function conformations.
Nakatogawa
Hitoshi
H
Institute for Virus Research and CREST, Japan Science and Technology Corporation, Kyoto University, Kyoto 606-8507, Japan.
Murakami
Akiko
A
Mori
Hiroyuki
H
Ito
Koreaki
K
D000251:Adenosine Triphosphatases / Q000096:biosynthesis / Q000502:physiology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000502:physiology*; D010957:Plasmids; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D014157:Transcription Factors / Q000502:physiology*
D001426:Bacterial Proteins; D017931:DNA Primers; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C497347:SecM protein, E coli; D014157:Transcription Factors; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins