3 HOMOLOGS OF RDS PERIPHERIN IN XENOPUS-LAEVIS PHOTORECEPTORS THAT EXHIBIT COVALENT AND NONCOVALENT INTERACTIONS/

We have isolated and characterized three homologs of mammalian rds/per ipherin from Xenopus retinae. One (xrds38) is likely the Xenopus ortho log, while the other two (xrds36 and -35) are more distant relatives. By immunocytochemical analysis of retinal sections, xrds38 is distribu ted in both rod and cone photoreceptors, while xrds36 and xrds35 are p resent in rods only. At the EM level, xrds38 is present specifically i n the rims and incisures of rod and cone outer segment discs. All are N-glycosylated and form covalent dimers. Immunoprecipitation analysis showed that in rods, these three proteins interact to form heterotetra meric or higher-order complexes. The pattern of sequence conservation among the xrds proteins, mammalian rds/peripherin, and mammalian rom-l suggest that the central portion of the intradiscal D2 loop contains the interacting structural elements.