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Inhibitory effect of acidic pH on OmpC porin: wild‐type and mutant studies
Author(s) -
Liu Nazhen,
Delcour Anne H
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00975-2
Subject(s) - porin , mutant , chemistry , wild type , biochemistry , biophysics , biology , gene , bacterial outer membrane , escherichia coli
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.