title: Ring-like pore structures of SecA: implication for bacterial protein-conducting channels.
abstract: SecA, an essential component of the general protein secretion pathway of bacteria, is present in Escherichia coli as soluble and membrane-integral forms. Here we show by electron microscopy that SecA assumes two characteristic forms in the presence of phospholipid monolayers: dumbbell-shaped elongated structures and ring-like pore structures. The ring-like pore structures with diameters of 8 nm and holes of 2 nm are found only in the presence of anionic phospholipids. These ring-like pore structures with larger 3- to 6-nm holes (without staining) were also observed by atomic force microscopic examination. They do not form in solution or in the presence of uncharged phosphatidylcholine. These ring-like phospholipid-induced pore-structures may form the core of bacterial protein-conducting channels through bacterial membranes.
authors.affiliation: Department of Biological Sciences and Biotechnology, State-Key Laboratory of Biomembranes, Tsinghua University, Beijing 100084, China.
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Hsiuchin
authors.initials: H
authors.lastname: Yang
authors.forename: Xianchuan
authors.initials: X
authors.lastname: Chen
authors.forename: Ming-Xing
authors.initials: MX
authors.lastname: Duan
authors.forename: Phang C
authors.initials: PC
authors.lastname: Tai
authors.forename: Sen-Fang
authors.initials: SF
authors.lastname: Sui
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D001426:Bacterial Proteins; D004926:Escherichia coli / Q000502:physiology* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D007473:Ion Channels / Q000737:chemistry; D008081:Liposomes; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D010743:Phospholipids / Q000737:chemistry; D011487:Protein Conformation; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007473:Ion Channels; D008081:Liposomes; D026901:Membrane Transport Proteins; D010743:Phospholipids; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins