IMPRINTING EFFECTS OF PROLINE-CONTAINING DIPEPTIDES (PROLINE GLYCINE,PROLINE-LEUCINE, PROLINE-VALINE AND THEIR RETRO VARIANTS) IN TETRAHYMENA - EVOLUTIONARY CONCLUSIONS

Proline-glycine, proline-leucine and proline-valine dipeptides and the ir retro variants were used in the experiments to study the effects of pretreatment (imprinting) in Tetrahymena, by investigating fluorescei n isothiocyanate (FITC)-conjugated peptide binding. The protozoan orga nism could differentiate between the proline-dipeptides containing dif ferent partner amino-acids and between the dipeptides having the amino acids in reversed positions. The effect of imprinting was positive or negative and this was dependent on the type of the partner amino acid and on its position. Pro-Gly and Pro-Leu induced positive imprinting (elevated FITC-dipeptide binding) and Pro-Val induced negative imprint ing (decrease of FITC-peptide binding). There was positive imprinting induction in two cases for the retro FITC-peptide and in one case for the FITC-conjugate of the imprinter peptide itself. The highest positi ve imprinting (almost 60% increase) was induced by Pro-Gly for FITC-Gl y-Pro. Considering earlier-chemotaxis-experiments, the results of the present-binding-studies run parallel with the physiological effects. T he experiments call attention to the sharp differentiating ability of small peptides at a unicellular level, that could have some role in th e selection of molecules for hormone formation, during evolution.