Cromwell Road, London, SW7 5BD, UK ("Author for correspondence: tel +44 (0)20 8332 5379; email [email protected]) References Altschul SF. Madden TL.SchafferAA, ZhangJH, Zhang Z, Miller W, Lipman DJ. 1997. Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Met Renard,