Modes of Accessing Bicarbonate for the Regulation of Membrane Guanylate Cyclase (ROS-GC) in Retinal Rods and Cones.

ABSTRACT: The membrane guanylate cyclase, ROS-GC, that synthesizes cyclic GMP for use as a second messenger for visual transduction in retinal rods and cones, is stimulated by bicarbonate. Bicarbonate acts directly on ROS-GC1, because it enhanced the enzymatic activity of a purified, recombinant fragment of bovine ROS-GC1 consisting solely of the core catalytic domain. Moreover, recombinant ROS-GC1 proved to be a true sensor of bicarbonate, rather than a sensor for CO2. Access to bicarbonate differed in rods and cones of larval salamander, Ambystoma tigrinum, of unknown sex. In rods, bicarbonate entered at the synapse and diffused to the outer segment, where it was removed by Cl--dependent exchange. In contrast, cones generated bicarbonate internally from endogenous CO2 or from exogenous CO2 that wa

SUBMITTER: Makino CL 

PROVIDER: S-EPMC6378327 | biostudies-literature | 2019 Jan-Feb

REPOSITORIES: biostudies-literature