title: alpha-lytic protease can exist in two separately stable conformations with different His57 mobilities and catalytic activities.
abstract: alpha-Lytic protease is a bacterial serine protease widely studied as a model system of enzyme catalysis. Here we report that lyophilization induces a structural change in the enzyme that is not reversed by redissolution in water. The structural change reduces the mobility of the active-site histidine residue and the catalytic activity of the enzyme. The application of mild pressure to solutions of the altered enzyme reverses the lyophilization-induced structural change and restores the mobility of the histidine residue and the enzyme's catalytic activity. This effect of lyophilization permits a unique opportunity for investigating the relationship between histidine ring dynamics and catalytic activity. The results demonstrate that His57 in resting enzymes is more mobile than previously thought, especially when protonated. The histidine motion and its correlation to enzyme activity lend support to the reaction-driven ring flip hypothesis.
authors.affiliation: Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: Kristin Coffman
authors.initials: KC
authors.lastname: Haddad
authors.forename: James L
authors.initials: JL
authors.lastname: Sudmeier
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Bachovchin
authors.forename: William W
authors.initials: WW
authors.lastname: Bachovchin
mesh_terms: D002384:Catalysis; D005612:Freeze Drying; D006863:Hydrogen-Ion Concentration; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature
chemical_list: D012697:Serine Endopeptidases; C021826:myxobacter alpha-lytic proteinase