PHOTOCHEMICAL BINDING OF PHENOTHIAZINES ON BIOLOGICAL MEMBRANE PROTEINS

Abstract— The photobinding of phenothiazine derivatives (chlorpromazine, fluphenazine, promazine and promethazine) was studied on four different types of biological membranes (microsomes, myelin and synaptosomes from rat brain as well as human erythrocytes). The photoreaction was performed by ultraviolet irradiation of the tritiated compounds in their long wavelength absorption band (313 nm) and bound photoproducts were analysed by autoradiography of the proteins separated by polyacrylamide gel electrophoresis. The specificity of binding is low, however, a 34000 dalton band is intensely labeled on synaptic membranes with chlorpromazine and fluphenazine. All the phenothiazines bind on erythrocyte membrane proteins and specially on band 4.2 and on a peptide located before actin on the electrophoresis gel. These results show the generality of the phenothiazine photobinding on membrane proteins. These photobinding properties can be used for the identification and localization of some of these proteins.