Isolation of a cDNA Encoding a Kex2-like Endoprotease with Homology to furin from the Nematode Caenorhabditis elegans

A cDNA was isolated from the nematode Caenorhabditis elegans that encodes an endoprotease which is a member of the Kex2 family of serine endoproteases. Degenerate oligonucleotide primers were designed based on conserved regions within the active sites of known Kex2-like endoproteases, and were used for reverse transcription-polymerase chain reaction (RT-PCR) of poly(A)⁺RNA isolated from C. elegans. A PCR product was isolated that had homology to the active sites of known furin endoproteases, and was used as a probe to screen a C. elegans cDNA library. A Kex2-like endoprotease (CelfurPC) which encoded a 692-amino-acid preproendoprotease, was identified. The deduced amino acid sequence for the catalytic domain of CelfurPC is homologous to the known Kex2-like endoproteases, with strongest structural homology to the furin/PACE4 family. However, all furins and PACE4 proteins contain a characteristic cysteine-rich domain, and all furins contain a transmembrane domain, neither of which is present in the CelfurPC protein. CelfurPC may thus represent a new class of Kex2-like endoprotease.