Ring-like pore structures of SecA: implication for bacterial protein-conducting channels.
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.
Wang
Hong-Wei
HW
Department of Biological Sciences and Biotechnology, State-Key Laboratory of Biomembranes, Tsinghua University, Beijing 100084, China.
Chen
Yong
Y
Yang
Hsiuchin
H
Chen
Xianchuan
X
Duan
Ming-Xing
MX
Tai
Phang C
PC
Sui
Sen-Fang
SF
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
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