Preprotein translocase subunit SecB. SecB is a cytoplasmic component of the multisubunit membrane-bound enzyme termed Sec protein translocase, which is the main constituent of the General Secretory (type II) Pathway involved in translocation of nascent polypeptides across the cytoplasmic membrane. SecB has been shown to function as export-specific molecular chaperone that selectively binds preproteins, maintains them in a translocation competent state and delivers them to SecA, the membrane-bound ATPase, that drives the translocation reaction. In solution, SecB exists as homotetramer, which is organized as a dimer of dimers.
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