SEQUENCE OF A HUMAN CDNA-ENCODING PHOSPHATIDYLINOSITOL TRANSFER PROTEIN AND OCCURRENCE OF A RELATED SEQUENCE IS WIDELY DIVERGENT EUKARYOTES

Phosphatidylinositol (PtdIns) transfer protein (PtdInsTP) is a phospho lipid transfer protein that has been detected in all mammalian tissues examined. It catalyzes the transfer in vitro of PtdIns and phosphatid ylcholine between membranes in a number of natural and artificial memb rane systems and may be involved in secretion in vivo. In previous stu dies, we isolated and sequenced a cDNA encoding a rat PtdInsTP. A rat cDNA probe was used to isolate clones from a lambda gt11 human testis cDNA library which encoded full-length human PtdInsTP. The cDNA sequen ce defines a 270-amino-acid, 31.8-kDa protein whose sequence shares 98 .9% identity to that of rat, making it one of the most conserved prote ins known between the two species. DNA blot hybridization studies sugg est that there may be more than one gene encoding this protein in huma ns. A comparison of rat and human PtdInsTP cDNAs revealed strong seque nce similarity (88 and 84%) in portions of the corresponding 5'- and 3 '-untranslated regions (UTR) of the rat and human mRNAs.