3.3 | Analysis of amino acid mutations
In this study, the amino acid mutations of the VP2 protein were
identified, and the amino acid sequences of 44 isolates were compared
with reference strains (Table 2). The results showed that 43 isolates
had Phe267Tyr and Tyr324Ile mutations, and all new CPV-2a and new CPV-2b
strains identified in this study had the Thr440Ala substitution. The
substitutions of Ala5Gly and Gln370Arg were found in all CPV-2c subtype
isolates, which have been reported to be specific to the CPV-2c virus
(Geng et al., 2015). Of the 31 CPV-2c strains, only one showed a unique
substitution on Arg481Lys. Residue 481 is located in the greatest
variable GH loop (loops 3 and 4), comprising aa 267–498 of the VP2
protein (Agbandje, Parrish*, & Rossmann, 1995).