Gene isolation and prediction of the corresponding three-dimensional structure of subtilisin from the psychrophilic yeast, Glaciozyma antarctica PI12

Abstract

Aims: Subtilisin, a serine protease, is a key player in many industrial applications especially in the detergent industry. Most reported subtilisins originate from mesophilic and thermophilic microorganisms. Only scarce information about cold-active subtilisins from psychrophilic microbes is available. Here we describe the isolation, cloning and in silico characterisation of a gene encoding subtilisin in the obligate psychrophilic yeast, Glaciozyma antarctica PI12. Methodology and results: A full-length cDNA from Glaciozyma antarctica encoding subtilisin (GaSUB) was isolated through Reverse-Transcription-Polymerase Chain Reaction (RT-PCR) techniques. The open reading frame of GaSUB comprised 1,125 nucleotides encoding 375 amino acids. The GaSUB amino acid sequence had 49% sequence identity with a subtilisin from the yeast, Puccinia striiformis. Bioinformatic analyses revealed that the GaSUB protein contains a domain that represents the S8 domain of the largest protease family. The predicted model of GaSUB protein using MODELLER and Pymol software revealed that this enzyme has longer loops and less intramolecular interactions between amino acid residues as compared to its mesophilic and thermophilic counterparts. These characteristics are known to help in protein flexibility and stability in cold-active enzymes. Conclusion, significance and impact of study: Bioinformatics characterisations suggested that this enzyme is uniquely adapted to cold environments. Further work using amplified cDNA will be conducted to confirm the catalytic function of this enzyme.