Visual arrestin binding to rhodopsin. Intramolecular interaction between the basic N terminus and acidic C terminus of arrestin may regulate binding selectivity.
Visual arrestin plays an important role in quenching phototransduction via its ability to preferentially bind to phosphorylated light-activated rhodopsin (P-Rh*). Recently we proposed a mechanism for the binding of visual arrestin to P-Rh* that helps to explain the nature of the conformational changes in arrestin observed upon binding. This mechanism involves a multisite interaction between arrestin and P-Rh* and implies an interaction between the C-terminal and N-terminal domains of arrestin. To obtain further insight into the mechanism of arrestin-rhodopsin interaction we have characterized the ability of polyanions to inhibit the interaction of wild type and mutant arrestins to different functional forms of rhodopsin. These studies reveal that: 1) heparin is most potent at inhibiting arrestin binding to dark phosphorylated rhodopsin > light-activated rhodopsin > P-Rh*; 2) C-terminal deletions in arrestin increase arrestin sensitivity to heparin inhibition while an N-terminal deletion (residues 2-16) decreases heparin inhibition; 3) the sensitivity of chimeric arrestins to heparin inhibition is determined by the origin of the N terminus of the chimera; and 4) heparin also inhibits arrestin binding to truncated 329G-Rh*, suggesting it does not mimic the phosphorylated C terminus of rhodopsin. Taken together, these data suggest that heparin mimics the regulatory acidic C terminus of arrestin. Since the basic N-terminal region of arrestin appears to serve as a site of heparin binding it is a likely candidate to be involved in the intramolecular interaction with the C-terminal region. The interaction of the N- and C-terminal domains of arrestin may control the conformational rearrangements in arrestin that occur upon binding to P-Rh*.
Gurevich
V V
VV
Department of Pharmacology, Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
Chen
C Y
CY
Kim
C M
CM
Benovic
J L
JL
D000818:Animals; D000838:Anions; D000941:Antigens / Q000378:metabolism*; D019393:Arrestin; D002417:Cattle; D004252:DNA Mutational Analysis; D005136:Eye Proteins / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D008027:Light; D046911:Macromolecular Substances; D010833:Phytic Acid / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011994:Recombinant Proteins; D012243:Rhodopsin / Q000378:metabolism*; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
D000838:Anions; D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D010833:Phytic Acid; D006493:Heparin; D012243:Rhodopsin