<i>In situ</i> opening/closing of OmpG from <i>E</i>. <i>coli</i> and the splitting of β-sheet signals in ATR-FTIR spectroscopy

Abstract

The pH dependent opening and closure of Escherichia coli OmpG is driven by the formation and breaking of hydrogen bridges in beta-strands S11-S13. We have investigated the in situ secondary structural changes of OmpG with ATR-FTIR difference spectroscopy in order to detect the signals associated with the newly established interactions. Curve-fitting of OmpG in two pH conditions revealed the splitting and shifting of beta-sheet signals upon opening of the channel. Besides secondary structure changes, there are also amino acid side chain signals that play active role in opening/closing of the channel. An interaction among positively charged arginines and negatively charged aspartic and glutamic acid residues is suggested upon closure of the channel while this interaction is abolished when the channel opens at higher pH. (C) 2012 Elsevier B.V. All rights reserved.