Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Cell Biology, SecA, Protein translocase, SecYEG, Preproteins, ATPase, Motor protein, SIGNAL RECOGNITION PARTICLE, PEPTIDE-BINDING DOMAIN, IN-VITRO TRANSLOCATION, RNA HELICASE ACTIVITY, COLI TRIGGER FACTOR, X-RAY-STRUCTURE, ESCHERICHIA-COLI, CRYSTAL-STRUCTURE, ATPASE SECA, MEMBRANE-PROTEIN, Adenosine Triphosphatases, Bacterial Proteins, Cell Membrane, Escherichia coli, Escherichia coli Proteins, Membrane Transport Proteins, Molecular Motor Proteins, Protein Binding, Protein Transport, SEC Translocation Channels, SecA Proteins, 02 Physical Sciences, 06 Biological Sciences, 31 Biological sciences, 51 Physical sciences

Abstract:

More than 30years of research has revealed that the dynamic nanomotor SecA is a central player in bacterial protein secretion. SecA associates with the SecYEG channel and transports polypeptides post-translationally to the trans side of the cytoplasmic membrane. It comprises a helicase-like ATPase core coupled to two domains that provide specificity for preprotein translocation. Apart from SecYEG, SecA associates with multiple ligands like ribosomes, nucleotides, lipids, chaperones and preproteins. It exerts its essential contribution in two phases. First, SecA, alone or in concert with chaperones, helps mediate the targeting of the secretory proteins from the ribosome to the membrane. Next, at the membrane it converts chemical energy to mechanical work and translocates preproteins through the SecYEG channel. SecA is a highly dynamic enzyme, it exploits disorder-order kinetics, swiveling and dissociation of domains and dimer to monomer transformations that are tightly coupled with its catalytic function. Preprotein signal sequences and mature domains exploit these dynamics to manipulate the nanomotor and thus achieve their export at the expense of metabolic energy. This article is part of a Special Issue entitled: Protein Trafficking & Secretion.