Mutation-deletion analysis of a Ca(2+)-dependent phospholipid binding (CaLB) domain within p120 GAP, a GTPase-activating protein for p21 ras.

摘要: Abstract p120 GAP is a GTPase activating protein for p21 ras. It multidomain which exhibits sequence similarity with other GTPase-activating proteins, src, pleckstrin and central portion of the kinase C conserved region 2 domain known as CaLB (Ca(2+)-dependent phospholipid-binding). The presence this motif has led to speculation that p120 may be member family structurally related proteins containing Ca(2+)-dependent membrane/lipid-binding domain. Here we have studied in vitro phospholipid-binding properties isolated proposed human deduce indeed located between amino acids 606 648. Binding phosphatidylserine phosphatidylinositol, but not phosphatidylcholine, within Ca(2+)-dependent, an estimated EC50 Ca2+ approx. 1 microM. Using deletion-mutation analysis further defined minimal boundaries activity. 612-643 exhibit full activity, deletion either 612-617 or 633-648 significantly decreased abolished phospholipid binding. These studies establish constitute functional thereby imply role regulation association cellular (membrane) phospholipids.