1. MRC Centre for Molecular and Cellular Biology, Department of Biomedical Sciences, Faculty of Health Sciences, University of Stellenbosch, P.O. Box 19063, Tygerberg 7505, South Africa
2. Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
3. Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535, South Africa