Analyses of sequences of the amplified products were carried using BioEdit Sequence Alignment Editor Software (version 6.0.5) (http://www.mbio .ncsu.edu/BioEdit/bioedit.html). The pI and charge values of the coat protein were calculated using the protein calculator developed by Chris Putnam of The Scripps Research Institute (http://www. scripps.edu/∼cdputnam/protcalc.html).