Identification of human neurophysins: complete amino acid sequences of MSEL- and VLDV-neurophysins.

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Abstract
Two human neurophysins were purified from acetone-desiccated posterior pituitaries by acidic extraction, molecular sieving and ion-exchange chromatography. The complete amino acid sequence of each protein was determined by using a sequencer and characterizing 2 sets of overlapping enzymic peptides. The 2 neurophysins belong to 2 structural families previously defined as MSEL- and VLDV-neurophysins according to the nature of the residues in positions 2, 3, 6 and 7. (MSEL-neurophysins contain methionine-2, serine-3, glutamic acid-6, and leucine-7; VLDV-neurophysins contain valine-2, leucine-3, aspartic acid-6, and valine-7). Human MSEL-neurophysin has only 93 residues instead of 95 usually found in MSEL-neurophysins from other mammalian species, probably because of a deletion of amino acids 91 and 92. Compared with bovine MSEL-neurophysin, 9 variations (7 substitutions and 2 deletions) are observed. Human VLDV-neurophysin has 93 residues, as do the other mammalian VLDV-neurophysins. There are 11 substitions when the comparison is made with bovine VLDV-neurophysin. Between the 2 human neurophysins, there are 26 variations. However, the central parts of the proteins (residues 10-70) are nearly identical. In this region identical substitutions are found in positions 29 and 60 of both neurophysins, suggesting either a single exon or some relationship between the 2 corresponding genes.