HtrA Heat Shock Protease Interacts with Phospholipid Membranes and Undergoes Conformational Changes

摘要: The HtrA (DegP) protein of Escherichia coli is a heat shock serine protease, essential for cell survival only at temperatures above 42°C. It has been shown by genetic experiments that an envelope functioning in the periplasmic space. To clarify cellular localization HtrA, E. cells were fractionated, and was not detected immunoblotting technique periplasm or fraction soluble proteins but found inner membrane. could be partially eluted from total membrane high ionic strength solution, whereas solutions affecting conformation released almost completely. These results, taken together with evidence showing functions periplasm, indicate peripheral protein, localized on side As first step toward solving problem HtrA-membrane interactions, structure presence phosphatidylglycerol (PG), phosphatidylethanolamine (PE), cardiolipin (CL) analyzed fluorescence Fourier-transform infrared spectroscopy. data indicated interaction PG CL PE suspensions. Fluorescence spectroscopy revealed this level polar head group phospholipid. In PG/HtrA system, small changes observed secondary remarkable decrease thermal stability which suggested tertiary structure. This suggestion supported showed shift emission spectrum tyrosine residues reduced intensity, phenomena Infrared also leads to protection unfolded against aggregation relatively low temperatures. conformational influenced proteolytic activity increasing it 37–45°C inhibiting 50–55°C. inhibited all tested.