Preliminary X-ray analysis of a C2-like domain from protein kinase C-delta

C2 domains are intracellular modules of approximately 130 residues that are found in many proteins involved in membrane trafficking and signal transduction. They are known to serve a variety of roles including binding ligands such as calcium, phospholipids and inositol polyphos-phates as well as interacting with larger macromolecules. Although originally identified in the Ca2+-dependent protein kinase C isoforms (PKC), initially no C2 domain was evident within the Ca2+-independent isoenzymes. A recent study identified a divergent C2 domain in several novel, Ca2+-independent PKCs (delta, epsilon, eta and straight theta), located at their N-termini in a region previously referred to as a variable domain zero (Vo) [Ponting & Parker (1996). Protein Sci. 5, 2375-2390]. The functional importance of this domain in the context of the novel PKCs is at present not well understood though it has been implicated in substrate recognition. The expression, crystallization and preliminary crystallographic analysis of recombinant Vo domain (residues 1-123) from PKC-delta is reported here. Crystals were obtained from incomplete factorial screens after removal of the histidine tag used to aid purification. These crystals diffracted to Bragg spacings of approximately 3 A using a rotating-anode source and to 1.9 A using synchrotron radiation. The crystals have cell parameters of a = 60.7, b = 120.9 and c = 40.7 A and systematic absences consistent with the orthorhombic space group P212121. To facilitate structure determination we have prepared, characterized and crystallized selenomethionine-substituted material.