Synthesis and biological activity of amino terminus extended analogues of the .alpha. mating factor of Saccharomyces cerevisiae

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Abstract
The synthesis and biological activity are reported for extended analogues of the secreted tridecapeptide .alpha.-factor (Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr) from Saccharomyces cervisiae. Peptides with Ala, Glu-Ala, Ala-Glu-Ala, or Glu-Ala-Glu-Ala attached to the amino terminis of .alpha.-factor were synthesized by the solid-phase method on a (phenylacetamido)methyl (PAM) resin, using a combination of dicyclohexylcarbodiimide- and 1-hydroxybenzotriazole-accelerated active ester coupling procedures. Free peptides were obtained by hydrogen fluoride (HF) cleavage in the presence of appropriate scavengers. Normal high HF cleavage and "low-high" HF cleavage were equally effective in liberating the desired product from the PAM resin. Yields of pure peptide ranged from 9% to 17%. All of the extended .alpha.-factors, which represent sequences of pro-.alpha.-factor coded for in the MF.alpha.1 structural gene, caused morphological aberrations (shmoo assay) in strain X2180-1A (MATa) the same as those caused by the tridecapeptide. The 14-peptide was equally active compared to the native .alpha.-factor whereas the 17-peptide was 5-10-fold less active. The analogues also arrested to various degrees (halo assay) the growth of S. cerevisiae RC629 (MATa sstl) and S. cerevisiae RC631 (MATa sst2), two supersensitive mutants, and were converted to pheromones of equal activity by treatment with V8 protease. A temperature-sensitive receptor mutant responded to all the peptides at the permissive but not the restrictive temperature. An .alpha.-factor antagonist, des-Trp1,Ala3-.alpha.-factor, inhibited activity of all extended peptides. These results confirm that all the extended peptides interact with the same receptor and that this receptor can accommodate additional residues at the amino terminus of the .alpha.-factor.

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