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Light-regulated photoreceptor phosphodiesterase

Thesis/Dissertation ·
OSTI ID:6940387

The primary function of the rod outer segment (ROS) is to transduce a photon signal into a cellular response. Two sites of cGMP interaction with the ROS phosphodiesterase have direct bearing on the mechanism of phototransduction. In addition to the phosphodiesterase catalytic site, high affinity non-catalytic sites occur that specifically bind cGMP. These non-catalytic binding sites, identified and partially characterized by photoaffinity labeling with {sup 32}P-cGMP, are present on both the {alpha} and {beta}-subunits, and their concentration was determined to exceed the total ROS cGMP content by 4-fold, suggesting a limited availability of cGMP for interaction with the phosphodiesterase catalytic site and the cation channel binding site. Binding of cGMP to these non-catalytic sites was reported by Yamazaki et al. to be inhibited by activation of G-protein, but the possibility was not eliminated that the G-protein-induced increase in phosphodiesterase activity may have limited the availability of cGMP for binding. In the present studies it was shown that this apparent inhibition of cGMP binding by G-protein can be entirely attributed to an increased hydrolysis of cGMP, that activated G-protein does not alter any parameter of these non-catalytic cGMP binding sites.

Research Organization:
Minnesota Univ., Minneapolis, MN (USA)
OSTI ID:
6940387
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CHEMICAL COMPOSITION
DAYS LIVING RADIOISOTOPES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENZYME ACTIVITY
ENZYMES
ESTERASES
HYDROLASES
ISOTOPES
KINETICS
LIGHT NUCLEI
MASSLESS PARTICLES
MEMBRANE PROTEINS
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHODIESTERASES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOTONS
PROTEINS
RADIATIONS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
VISIBLE RADIATION