Recognizing the pleckstrin homology domain fold in mammalian phospholipase D using hidden Markov models

Phospholipase D was first described in plant tissue but has recently been shown to occur in mammalian cells where it is activated by cell surface receptors. Its mode of activation by receptors in unclear. Biochemical studies suggest that it may occur downstream of other effector proteins and that small GTP-dependent regulatory proteins may be involved. The sequence in a non-designated region of mammalian phospholipase D1 and 2 shows similarity to a structural domain that is present in signalling proteins that are regulated by protein kinases or heterotrimeric G-proteins. Mammalian phospholipase D has structural similarities with other lipid signalling phospholipases and thus may be regulated by receptors in an analogous fashion. (C) 1999 Federation of European Biochemical Societies.