tailieunhanh - Báo cáo Y học: Domain V of m-calpain shows the potential to form an oblique-orientated a-helix, which may modulate the enzyme’s activity via interactions with anionic lipid

The activity of m-calpain, a heterodimeric, Ca 2+ -dependent cysteine protease appears to be modulated by membrane interactions involving oblique-orientated a-helix formation by a segment, GTAMRILGGVI, in the protein’s smaller subunit. Here, graphical and hydrophobic moment-based analyses predicted that this segment may form ana-helix with strong structural resemblance to the influenza virus peptide, HA2, a known oblique-orientateda-helix former. | Eur. J. Biochem. 269 5414-5422 2002 FEBS 2002 doi Domain V of m-calpain shows the potential to form an oblique-orientated a-helix which may modulate the enzyme s activity via interactions with anionic lipid Klaus Brandenburg1 Frederick Harris2 Sarah Dennison2 Ulrich Seydel1 and David Phoenix2 division of Biophysics Forschunginstitute Borstel Germany department of Forensic and Investigative Science University of Central Lancashire Preston UK The activity of m-calpain a heterodimeric Ca2 -dependent cysteine protease appears to be modulated by membrane interactions involving oblique-orientated a-helix formation by a segment GTAMRILGGVI in the protein s smaller subunit. Here graphical and hydrophobic moment-based analyses predicted that this segment may form an a-helix with strong structural resemblance to the influenza virus peptide HA2 a known oblique-orientated a-helix former. Fourier transform infrared spectroscopy showed that a peptide homologue of the GTAMRILGGVI segment VP1 adopted low levels of a-helical structure w 20 in the presence of zwitterionic lipid and induced a minor decrease 3 C in the gel to liquid-crystalline phase transition temperature TC of the hydrocarbon chains of zwitterionic membranes suggesting interaction with the lipid headgroup region. In contrast VP1 adopted high levels of a-helical structure 65 in the presence of anionic lipid induced a large increase 10 C in the TC of anionic membranes and showed high levels of anionic lipid monolayer penetration ASP mN-m 1 suggesting deep levels of membrane penetration. VP1 showed strong haemolytic ability LD50 mM but in the presence of ionic agents this ability and that of VP1 to penetrate anionic lipid monolayers was greatly reduced. In combination our results suggest that m-calpain domain V may penetrate membranes via the adoption of an oblique-orientated a-helix and electrostatic interactions. We speculate that these interactions may involve snorkelling by