A SPLICE VARIANT OF ARRESTIN - MOLECULAR-CLONING AND LOCALIZATION IN BOVINE RETINA

Inactivation of photolyzed rhodopsin requires phosphorylation of the r eceptor and binding of the 48-kDa regulatory protein arrestin. We rece ntly isolated a novel form of arrestin, termed p(44), that is truncate d at the COOH terminus (Palczewski, K., Buczylko, J., Ohguro, H., Anna n, R. S., Carr, S. A., Crabb, J. W., Kaplan, M. W, Johnson, R. S., and Walsh, K. A. (1994) Protein Sci. 3, 319-329) and strongly inhibits G( t) activation by non-phosphorylated rhodopsin. p(44) is identical to a rrestin except at the COOH terminus, where the 35 amino acids of arres tin are replaced by a single alanine residue. p(44) is identified as a splice variant of arrestin based on the identical cDNA sequence of p( 44) with arrestin (except the 3' non-coding regions), the presence of an exon/intron junction at the Ser(369) codon, and identical Southern hybridization patterns generated by the 3' non-coding portion of arres tin and p(44). Immunocytochemistry reveals that p(44) is localized in the photoreceptor outer segment, whereas arrestin is present throughou t the cell. This specificity of localization to the outer segment is p ersistent with a role of p(44) in the phototransduction cascade.