Differential stability of human interleukin 1 beta fragments expressed in yeast.

We have made deletions in a human interleukin 1 beta cDNA cloned in a yeast vector capable of directing the expression and secretion of foreign protein. Deletions at either the 5' or 3' end of the cDNA result in a dramatic drop in yield of protein. An investigation of some possible causes points to instability of the truncated peptides as a major factor contributing to low yield. The results suggest that correct folding of mature interleukin 1 into a protease resistant form requires almost the entire polypeptide.