title: Effects of signal peptide and adenylate on the oligomerization and membrane binding of soluble SecA.
abstract: SecA protein, a cytoplasmic ATPase, plays a central role in the secretion of signal peptide-containing proteins. Here, we examined effects of signal peptide and ATP on the oligomerization, conformational change, and membrane binding of SecA. The wild-type (WT) signal peptide from the ribose-binding protein inhibited ATP binding to soluble SecA and stimulated release of ATP already bound to the protein. The signal peptide enhanced the oligomerization of soluble SecA, while ATP induced dissociation of SecA oligomer. Analysis of SecA unfolding with urea or heat revealed that the WT signal peptide induces an open conformation of soluble SecA, while ATP increased the compactness of SecA. We further obtained evidences that the signal peptide-induced oligomerization and the formation of open structure enhance the membrane binding of SecA, whereas ATP inhibits the interaction of soluble SecA with membranes. On the other hand, the complex of membrane-bound SecA and signal peptide was shown to resume nucleotide-binding activity. From these results, we propose that the translocation components affect the degree of oligomerization of soluble SecA, thereby modulating the membrane binding of SecA in early translocation pathway. A possible sequential interaction of SecA with signal peptide, ATP, and cytoplasmic membrane is discussed.
authors.affiliation: Department of Biochemistry, College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
authors.forename: Ji Yeun
authors.initials: JY
authors.lastname: Shin
authors.forename: Mihee
authors.initials: M
authors.lastname: Kim
authors.forename: Taeho
authors.initials: T
authors.lastname: Ahn
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D033902:Periplasmic Binding Proteins / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D021382:Protein Sorting Signals; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008081:Liposomes; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033902:Periplasmic Binding Proteins; D021382:Protein Sorting Signals; C028003:RbsB protein, E coli; D000069816:SEC Translocation Channels; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins