Structural motif and characteristics of the extracellular domain of P-2X receptors

Seven sequences of the proteins recently cloned from rat tissues and identified as P-2X receptors are examined. Their putative transmembrane and extracellular domains and the most probable locations of disulphide bridges are discussed. Some surface accessible regions are identified and the structure of the putative ATP binding domain is discussed in the light of known selectivities and physiological characteristics of individual P-2X subunits. The summarised information and the theoretical considerations regarding the protein structure of P-2X receptors have been used to select amino acid sequences for raising antibodies against the P-2X1 receptor subunit, Initial results suggest that, in rat brainstem, P-2X1 receptor subunits are found on a distinct subpopulation of neuronal perikarya in distributions consistent with distributions of known alpha,beta-methylene-ATP autoradiography and physiological effects of purinoceptor activation. (C) 1997 Academic Press.