Residue L143 of the Foot-and-Mouth Disease Virus Leader Proteinase Is a Determinant of Cleavage Specificity
ABSTRACT The foot-and-mouth disease virus (FMDV) leader proteinase (Lpro) self-processes inefficiently at the Lpro/VP4 cleavage site LysLeuLys*GlyAlaGly (* indicates cleaved peptide bond) when the leucine at position P2 is replaced by phenylalanine. Molecular modeling and energy minimization identified the Lpro residue L143 as being responsible for this discrimination. The variant Lpro L143A self-processed efficiently at the Lpro/VP4 cleavage site containing P2 phenylalanine, whereas the L143M variant did not. Lpro L143A self-processing at the eIF4GII sequence AspPheGly*ArgGlnThr was improved but showed more-extensive aberrant processing. Residue 143 in Lpro is occupied only by leucine and methionine in all sequenced FMDV serotypes, implying that these bulky side chains are one determinant of the restricted specificity of Lpro.