SecA - a multidomain and multitask bacterial export protein.

Most bacterial secretory proteins destined to the extracytoplasmic space are secreted posttranslationally by the Sec translocase. SecA, a key component of the Sec system, is the ATPase motor protein, directly responsible for transferring the preprotein across the cytoplasmic membrane. SecA is a large protein, composed of several domains, capable of binding client preproteins and a variety of partners, including the SecYEG inner membrane channel complex, membrane phospholipids and ribosomes. SecA-mediated translocation can be divided into two major steps: (1) targeting of the preproteins to the membrane translocation apparatus and (2) transport across the membrane through the SecYEG channel. In this review we present current knowledge regarding SecA structure and function of this protein in both translocation steps. The most recent model of the SecA-dependent preprotein mechanical translocation across the bacterial cytoplasmic membrane is described. A possibility of targeting SecA with inhibitory compounds as a strategy to combat pathogenic bacteria will be discussed as well.