Analysis of a Novel Peptide That Is Capable of Inhibiting the Enzymatic Activity of the Protein Kinase A Catalytic Subunit-Like Protein from Trypanosoma equiperdum

Abstract

A peptide possessing the αN-helix motif of the protein kinase A (PKA) regulatory subunit-like protein from the Trypanozoom subgenera (VAP26) was shown to inhibit the enzymatic activity of the Trypanosoma equiperdumPKA catalytic subunit-like protein in a similar manner that the mammalian heat-stable soluble PKA inhibitor (PKI). However, VAP26 did not contain the PKI inhibitory sequence. Bioinformatics analyzes of the αN-helix motif from the Trypanozoon protein suggested that the sequence can form favorable peptide-protein interactions of hydrophobic nature with the PKA catalytic subunit-like protein, which could represent an alternative PKA inhibition mechanism. It was determined that the sequence of the αN-helix motif of the Trypanozoon protein is conserved but signi cantly divergent from the corresponding αN-helix motifs in the Leishmania and mammalian proteins. This sequence divergence contrasted with the secondary structure of the αN-helix motif, which appeared to be conserved in every regulatory subunit-like protein that was analyzed. In silico mutation experiments at positions I234, L238 and F244 of the αNhelix motif from the Trypanozoon protein destabilized both the speci c motif and the protein, while mutations at positions T239 and Y240, on the contrary, stabilized the motif and the protein. These results suggested that the αN-helix motif from the Trypanozoon protein probably possessed a different evolutionary path than its Leishmania and mammalian counterparts. Moreover, nding stabilizing mutations can be used for the design of novel inhibitory peptides on the basis of the αN-helix motif from the Trypanozoon PKA regulatory subunit-like protein.