Neuron-specific antigen HPC-1 from bovine brain reveals strong homology to epimorphin, an essential factor involved in epithelial morphogenesis: identification of a novel protein family.

We have already cloned the cDNA for the HPC-1 antigen, a neuron-specific protein antigen from the rat brain. Here we report the molecular cloning of the bovine HPC-1 antigen homologue, and much strong sequence conservation between rat and bovine. By searching the recent protein data base, it was found that the HPC-1 antigen revealed unusual similarity to epimorphin which was mesenchymal factor related to the morphogenesis of primitive epidermal tissues in embryonic stages. We also found that the HPC-1 antigen was identical to p35A (syntaxin) which bound both to a synaptic vesicle protein and to N-type calcium channel. Although the relationship of the physiological functions, structures and topologies along cellular membrane between the HPC-1 antigen and epimorphin have not been consistent yet, these two proteins belong to a novel protein family.