The genes encoding the MVPs from human, rat, electric ray and Dictyostelium have been cloned and sequenced (see Table I). All of the MVP genes isolated to date are single copy. The human MVP has been localized to the short arm of chromosome 16. Comparison of the deduced amino acid sequences of human and rat MVPs indicate that they share ~88% identity while they share about ~60% identity with either Dictyostelium MvpA or MvpB. Interestingly, Dictyostelium MvpA and MvpB proteins share only ~60% identity, indicating that they are as related to each other as to the rat and human MVPs. MvpB is more acidic than MvpA. It is possible that the divergent regions of these two proteins might have arisen to functionally substitute for the lack of p240 or p193 homologs in this organism.