Bioinformatics analysis of the αN-helix motif of the Trypanozoon protein kinase A regulatory subunit-like protein, which is capable of inhibiting the enzymatic activity of the protein kinase A catalytic subunit-like protein

Abstract

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 significantly 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 αN-helix motif from the Trypanozoon protein destabilized both the specific 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, finding 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.