Structure of the C2 domain from novel protein kinase C epsilon. A membranebinding model for Ca (2+)-independent C2 domains

Protein kinase C epsilon (PKC epsilon) is a member of the novel PKCs which are activated by acidic phospholipids, diacylglycerol and phorbol esters, b ut lack the calcium dependence of classical PKC isotypes. The crystal struc tures of the C2 domain of PKC epsilon, crystallized both in the absence and in the presence of the two acidic phospholipids, 1,2-dicaproyl-sn-phosphat idyl-L-serine (DCPS) and 1,2-dicaproyl-sn-phosphatidic acid (DCPA), have A resolution, respectively. The now been determined at 2.1, 1.7 and 2.8 Angst rom resolution, respectively. The central feature of the PKC epsilon -C2 do main structure is an eight-stranded, antiparallel, beta -sandwich with a ty pe II topology similar to that of the C2 domains from phospholipase C and f rom novel PKC delta. Despite the similar, topology, important differences a re found between the structures of C2 domains from PKCs delta and epsilon, suggesting they be considered as different PKC subclasses. Site-directed mu tagenesis experiments and structural changes in the PKC epsilon -C2 domain from crystals with DCPS or DCPA indicate, though phospholipids were not vis ible in these structures, that loops joining strands beta1-beta2 and beta5- beta6 participate in the binding to anionic membranes. The different behavi or in membrane-binding and activation between PKC epsilon and classical PKC s appears to originate in localized structural changes, which include a maj or reorganization of the region corresponding to the calcium binding pocket in classical PKCs. A mechanism is proposed for the interaction of the PKC epsilon -C2 domain with model membranes that retains basic features of the docking of C2 domains from classical, calcium-dependent, PKCs. (C) 2001 Aca demic Press.