Crystallization of a complex of Caenorhabditis elegans diadenosine tetraphosphate hydrolase and a non-hydrolysable substrate analogue, AppCH2ppA.

The molecule diadenosine tetraphosphate (Ap(4)A) has been suggested to be a component of the cellular response to metabolic stress and/or, via the intracellular Ap(3)A/Ap(4)A ratio, to be involved in differentiation and apoptosis. Thus, the enzyme Ap(4)A hydrolase has a key metabolic role through regulation of the intracellular Ap(4)A levels. Crystals of this enzyme from the nematode Caenorhabditis elegans have been obtained in the presence of a non-hydrolysable substrate analogue, AppCH(2)ppA. The crystals belong to space group P2(1), unit-cell parameters a = 57.6, b = 36.8, c = 68.9 A, beta = 114.2 degrees, and diffract to approximately 2.0 A. Determination of the structure of this complex will provide insights into the substrate specificity and catalytic activity of this class of enzymes.