Effects of dipeptides containing the amino acid, proline on the chemotaxis of Tetrahymena pyriformis. Evolutionary conclusions on the formation of hormone receptors and hormones.

Our investigations demonstrate that proline-containing dipeptides can provoke a chemosensory response from the unicellular Tetrahymena pyriformis. The chemotactic effects of the dipeptides have a close relationship with the side chain and the lipophilicity of the amino-terminal amino acid. Comparison of 'mirror' variants of proline-containing dipeptides points to the fact that dipeptides with small side chain and non-polar character amino acids (Gly-Pro, Ala-Pro) are preferred on the amino-terminal end. In the case of amino acids with very variable side chains, small (Pro-Gly) and the large side chain and non-polar character amino acids (Pro-Leu, Pro-Phe) on the carboxyl-terminal end can induce significant chemotactic responses. With valine on any terminus the proline-containing dipeptide induced a weak repellent effect.