THE PRO-REGION OF THE KEX2 ENDOPROTEASE OF SACCHAROMYCES-CEREVISIAE IS REMOVED BY SELF-PROCESSING

We have produced in the baculovirus/insect cells expression system a soluble secreted form of the Saccharomyces cerevisiae Kex2 endoprotease. This secreted enzyme was purified and its NH2-terminal sequence determined. The NH2-terminal sequence started at residue Leu109 of the sequence deduced from the KEX2 gene nucleotide sequence, showing that the Kex2 enzyme is produced as a proenzyme. Residue Leu109 is preceded by a pair of basic amino acid residues (Lys107-Arg108) which is a potential processing site for the Kex2 endopeptidase. Futhermore, expression of an inactive form of this truncated enzyme resulted in the production of a protein with a higher molecular weight. These observations suggest that the pro-region of Kex2 endoprotease is removed by a self-processing event.