title: Role of membrane potential in protein folding and domain formation during secretion in Escherichia coli.
abstract: The synthesis and processing of the periplasmic components of the leucine transport system of E coli have been studied to determine the role played by transmembrane potential in protein secretion. Both the leucine-isoleucine-valine binding protein and the leucine-specific binding protein are synthesized as precursors with 23 amino acid N-terminal leader sequences. The processing of these precursors is sensitive to the transmembrane potential. Since the amino acid sequence and the crystal structure have been determined for the leucine-isoleucine-valine binding protein, it and the closely related leucine-specific binding protein represent convenient models in which to examine the mechanism of protein secretion in E coli. A model for secretion has been proposed, suggesting a role for transmembrane potential. In this model, the N-terminal amino acid sequence of the precursor is assumed to form a hairpin of two helices. The membrane potential may orient this structure to make it accessible to processing. In addition, the model suggests that a negatively charged, folded domain of the secretory protein may electrophorese toward the trans-positive side of the membrane, thus providing an additional role for the transmembrane potential.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D008564:Membrane Potentials; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C488923:LivJ protein, E coli; C024913:LivK protein, E coli; D033902:Periplasmic Binding Proteins; C028332:leucine-isoleucine-valine binding protein, bacteria