CLONING AND FUNCTIONAL-ANALYSIS OF C-ELEGANS 7B2

The neuroendocrine protein 7B2 is a binding protein for the prohormone convertase 2 (PC2) and is required for the intracellular conversion o f proPC2 to active PC2, Both full-length 7B2 and its carboxy-terminal 31-residue peptide (CT peptide) are capable of potent inhibition of PC 2; the 7B2 protein thus regulates both the biosynthesis and the activi ty of PC2. Vertebrate 7B2s are highly conserved (92%-97% homology), an d thus, species comparison has not been informative in assessing the c rucial protein domains responsible for bioactivity, We here report the cloning of the Caenorhabditis elegans 7B2 protein. Although weakly co nserved with the vertebrate sequences (23% similarity with mouse 7B2), C. elegans 7B2 contains the signature PPNPCP motif as well as a highl y conserved heptapeptide within the CT peptide. In in vitro assays, C. elegans 7B2 possessed significant inhibitory activity against recombi nant vertebrate PC2 (IC50 130 nhl), and in two functional tests, the a mino-terminal domain of C, elegans 7B2 facilitated the activation of p roPC2, We conclude that despite low amino acid conservation overall, b oth functional domains within 7B2 have been conserved between the C, e legans and the vertebrate proteins.