The Effect of Proteolytic Removal of the C-Terminal Fragment of Rhodopsin on Its Ability to Activate Visual Cascade |
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Authors: | Komolov K. E. Senin I. I. Filippov P. P. |
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Affiliation: | (1) Department of Enzymology, Belozerskii Research Institute of Physicochemical Biology, Moscow State University, Vorob'evy gory, Moscow, 119899, Russia |
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Abstract: | The role of the C-terminal domain of rhodopsin in the activation of transducin was studied. The treatment of photoreceptor membranes with trypsin, thermolysin, and Asp-N-endoprotease led to the respective rhodopsin species devoid of 9, 12-, or 19-aa C-terminal fragments. It was shown that the removal of 9-aa fragment by trypsin does not affect the catalytic activity of the receptor, whereas the thermolysin-induced truncation of the rhodopsin C-terminus by 12 aa about 1.5-fold enhances its activity. The Asp-N-endoprotease-assisted removal of 19 aa (i.e., the shortening by seven more C-terminal aa) virtually unchanges catalytic activity of the resulting truncated rhodopsin compared to the preparation truncated with thermolysin. These results suggest that the part of the rhodopsin C-terminal fragment between the sites of its cleavage by trypsin and thermolysin (Val337–Ser338–Lys339) inhibits the signal transduction from rhodopsin to the next component of visual cascade. |
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Keywords: | cGMP phosphodiesterase phosphorylation photoreception proteolysis rhodopsin visual cascade |
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