Identification of a unique membrane receptor for adenosine 5',5"'-P1,P4-tetraphosphate.

Adenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) has been implicated as a modulator of cell stress. We have performed binding studies which indicate that membranes from all tissues tested bind tritium-labeled Ap4A. The characteristics of Ap4A binding were determined on brain membrane homogenates after development of an optimized in vitro filter-binding assay. Ap4A binding is specific for adenylated dinucleotides and for the length of the phosphate bridge. A Kd of 0.71 microM for Ap4A was determined.