Isolated and purified platelet voltage dependent calcium channel (VDCC) .alpha..sub.1 subunit polypeptides, and nucleic acid molecules encoding the same. Recombinant host cells, recombinant nucleic acids, and recombinant proteins are also disclosed, along with methods of producing each. Isolated and purified antibodies to platelet VDCC .alpha..sub.1 subunit polypeptides, and methods of producing the same, are also disclosed. Platelet VDCC .alpha..sub.1 subunit polypeptides have biological activity in calcium transport. Thus, therapeutic and diagnostic methods involving this activity are also disclosed.