Controlled expression and functional characterisation of SasG - a surface protein of Staphylococcus aureus

Abstract

Staphylococcus aureus colonises the moist squamous epithelium of the anterior nares. One of the adhesins likely to be responsible is the S. aureus surface protein G (SasG) which has sequence similarity with the proteins Pls (plasmin sensitive) of S. aureus and Aap (accumulation associated protein) of S. epidermidis. Expression of SasG by a laboratory strain of S. aureus could not be detected by Western immunoblotting. To enable investigation of SasG, the gene was cloned into two expression vectors, the IPTG-inducible pMUTIN4 and the tetracycline-inducible pALC2073 and was introduced into S. aureus. The level of induction from pMUTIN4 was poor and while induction from pALC2073 was strong, repression was leaky. Site-directed mutagenesis was utilised in order to improve both vectors.