Inhibitory effect of acidic pH on OmpC porin: wild‐type and mutant studies

FEBS Letters

Liu, Nazhen¹  Delcour, Anne H¹ 

[1] Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5513, USA

关键词: Channel;    Closing;    Modulation;    Outer membrane;    Escherichia coli;   

DOI  :  10.1016/S0014-5793(98)00975-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

By use of the patch clamp technique, we have compared the electrophysiological signature of OmpC porin channels at neutral and acidic pH. The perfusion of pH 5.4 buffer to the periplasmic side of excised patches promoted the closure or block of ∼20% of the open porins present in the patch without changes in their single channel conductance. Besides this effect on the main, long-lived open state, lowering the pH also suppressed the spontaneous transitions of channels to another distinct short-lived open state. The inhibitory effect on the opening kinetics was particularly visible in two mutants (K16Q and E109Q) in which transitions to the short-lived open state are enhanced by the mutations themselves at pH 7.2. On the other hand, the R124Q mutant responded to acidic pH by an increased gating to the short-lived open state. The results suggest that acidic pH stabilizes a closed state of OmpC porin, and that the pH sensitivity might be conferred in part by R124, but not by K16 or E109.

【 授权许可】

Unknown