Deciphering role of amino acids for the stability of Staphylococcus aureus lipase (SAL3).

Lipase from Staphylococcus aureus (SAL3) has been gaining attention because of its potential application in detergent industries against its thermostability and pH stability. It has been also used in synthesis of starch oleate recently. Protein engineering of SAL3 will give insight in development of better lipase for industrial applications. The present work aims at bringing out the role of amino acid residues in the stability of SAL3 using prosa2003 (Protein Structure Analysis) program. 127 amino acid residues were identified as structurally/strategically important for stability of the protein among the modeled 386 residues and further categorized into four classes. In the first class, 47 positions are predicted at which substitution of any one of these 47 positions by any other amino acids will lead to destabilization of the protein. The second class comprises of 33 positions which can be mutated by one corresponding amino acid without affecting the stability of the protein. The third class comprises of 21 positions which can be mutated by two corresponding amino acids without affecting the stability of the protein. The fourth class comprises of 26 positions which can be substituted by three corresponding amino acids without affecting the stability of the protein. Further five residues Glu9, Glu136, Phe286, Lys305 and Leu358 are identified in which substitution by any amino acid does not affect protein stability. Hence mutation can be carried out at these positions in the direction of increasing protein stability. In conclusion, this study prefigures well as a prototype for mutation and protein engineering studies of SAL3.