Molecular cloning of kpcA gene encoding a Kex2p-like endoprotease from Aspergillus nidulans

We cloned and sequenced a gene, kpcA (Kex2p-like proprotein convertase A), from a genomic library of Aspergillus nidulans. The kpcA gene encodes an 820-residue protein, named KpcA, which contains a putative subtilisin-like catalytic domain (residues 136-466) homologous to that of the subtilisin serine protease family. KpcA shows 56, 73, and 47% amino acid identities with Saccharomyces cerevisiae Kex2p, Aspergillus niger KexB, and mouse furin within the subtilisin-like catalytic domain, respectively. The sequences around the proposed active site Asp, His, and Ser residues of KpcA are similar to those of other Kex2p family members. The KpcA mRNA transcript with an expected size of approximately 2.8 kb was detected in A. nidulans. The substrate specificity of KpcA, expressed in CHO cells, is similar to that of A. niger KexB and yeast Kex2p. We conclude that KpcA is a resident Kex2p-like proprotein that processes endoprotease in A. nidulans.