tailieunhanh - Báo cáo khoa học: Effects of salt on the kinetics and thermodynamic stability of endonuclease I from Vibrio salmonicida and Vibrio cholerae

Adaptation to extreme environments affects the stability and catalytic effi-ciency of enzymes, often endowing them with great industrial potential. We compared the environmental adaptation of the secreted endonuclease I from the cold-adapted marine fish pathogenVibrio salmonicida(VsEndA) and the human pathogen Vibrio cholerae (VcEndA). | ỊFEBS Journal Effects of salt on the kinetics and thermodynamic stability of endonuclease I from Vibrio salmonicida and Vibrio cholerae 1 2 Ill2lll la 2 2 Laila Niiranen Bj0rn Altermark Bj0rn O. Brandsdal Hanna-Kirsti S. Leiros Ronny Helland Arne O. Smalas2 and Nils P. Willassen1 1 Department of Molecular Biotechnology Institute of MedicalBiology Faculty of Medicine University of Tromso Norway 2 Norwegian StructuralBiology Centre NorStruct Department of Chemistry Faculty of Science University of Tromso Norway Keywords endonuclease I kinetics salt adaptation thermodynamic stability Vibrio Correspondence N. P. Willassen Department of Molecular Biotechnology Institute of MedicalBiology Faculty of Medicine University of Tromso N-9037 Tromso Norway Fax 47 776 453 50 Tel 47 776 446 51 E-mail nilspw@ Received 24 October 2007 revised 14 December 2007 accepted 1 February 2008 doi Adaptation to extreme environments affects the stability and catalytic efficiency of enzymes often endowing them with great industrial potential. We compared the environmental adaptation of the secreted endonuclease I from the cold-adapted marine fish pathogen Vibrio salmonicida VsEndA and the human pathogen Vibrio cholerae VcEndA . Kinetic analysis showed that VsEndA displayed unique halotolerance. It retained a considerable amount of activity from low concentrations to at least M NaCl and was adapted to work at higher salt concentrations than VcEndA by maintaining a low Km value and increasing kcat. In differential scanning calorimetry salt stabilized both enzymes but the effect on the calorimetric enthalpy and cooperativity of unfolding was larger for VsEndA indicating salt dependence. Mutation of DNA binding site residues VsEndA Q69N and K71N VcEndA N69Q and N71K affected the kinetic parameters. The VsEndA Q69N mutation also increased the Tm value whereas other mutations affected mainly AHcal. The determined crystal structure of VcEndA N69Q