Cleavage specificity of human rhinovirus-2 2A protease for peptide substrates.

Substrate requirements of the human rhinovirus serotype-2 2A protease have been examined using synthetic peptides. A chromogenic peptide with a sequence of TRPIITTA-p-nitroanilide was found to be cleaved efficiently by the 2A protease with an apparent Km value of 95 microM, which allowed the protease activity to be monitored and measured continuously using a spectrophotometer. Competition cleavage assays reveal this peptide was cleaved over 10-fold more efficiently than the 16-mer peptide derived directly from its native processing site. On the basis of these data, we conclude that the P1' glycine residue is not absolutely needed for the 2A cleavage to occur and the essential residues required for the 2A activity would exist within the N-terminal side of the scissile bond.