Investigating the SecY plug movement at the SecYEG translocation channel.
Protein translocation occurs across the energy-conserving bacterial membrane at the SecYEG channel. The crystal structure of the channel has revealed a possible mechanism for gating and opening. This study evaluates the plug hypothesis using cysteine crosslink experiments in combination with various allelic forms of the Sec complex. The results demonstrate that the SecY plug domain moves away from the center of the channel toward SecE during polypeptide translocation, and further show that the translocation-enhancing prlA3 mutation and SecG subunit change the properties of channel gating. Locking the plug in the open state preactivates the Sec complex, and a super-active translocase can be created when combined with the prlA4 mutation located in the pore of the channel. Dimerization of the Sec complex, which is essential for translocase activity, relocates the plug toward the open position. We propose that oligomerization may result in SecYEG cooperative interactions important to prime the translocon function.
Tam
Patrick C K
PC
Department of Biochemistry & Molecular Biology, Faculty of Medicine, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.
Maillard
Antoine P
AP
Chan
Kenneth K Y
KK
Duong
Franck
F
D015153:Blotting, Western; D003432:Cross-Linking Reagents; D003545:Cysteine / Q000378:metabolism; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology; D000069816:SEC Translocation Channels
D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D046912:Multiprotein Complexes; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; C088616:SecG protein, E coli; C057841:SecY protein, E coli; D003545:Cysteine