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The Effect of Deleting a Putative Salt Bridge on the Properties of the Thermostable Subtilisin-Like Proteinase, Aqualysin I

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Aqualysin I, is a subtilisin-like serine proteinase, from the thermophilic bacterium Thermus aquaticus. It is predicted that the enzyme contains a salt bridge, D17-R259, connecting the N- and C-terminal regions of the enzyme. Previously we reported on the stabilizing effect of the incorporation of a salt bridge at a corresponding site in VPR, a related cold adapted enzyme from a marine Vibrio sp. Here we describe the effect of the reverse change, i.e. the elimination of the salt bridge on the thermal stability and kinetic properties of aqualysin I. Deletion of the putative salt bridge in the D17N mutant of the enzyme destabilized the enzyme by 8-9 °C in terms of T50%, determined by thermal inactivation and over 4°C in Tm, as measured from melting curves of the inhibited enzyme. The mutation, however, had no significant effect on the kinetic parameters of the enzyme under standard assay conditions.

Keywords: Aqualysin I; site directed mutagenesis; temperature adaptation; thermal stability; thermophilic

Document Type: Research Article


Publication date: June 1, 2011

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  • Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.

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