G proteins and phototransduction.
Phototransduction is the process by which a photon of light captured by a molecule of visual pigment generates an electrical response in a photoreceptor cell. Vertebrate rod phototransduction is one of the best-studied G protein signaling pathways. In this pathway the photoreceptor-specific G protein, transducin, mediates between the visual pigment, rhodopsin, and the effector enzyme, cGMP phosphodiesterase. This review focuses on two quantitative features of G protein signaling in phototransduction: signal amplification and response timing. We examine how the interplay between the mechanisms that contribute to amplification and those that govern termination of G protein activity determine the speed and the sensitivity of the cellular response to light.
Arshavsky
Vadim Y
VY
Howe Laboratory of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA. vadim_arshavsky@meei.harvard.edu
Lamb
Trevor D
TD
Pugh
Edward N
EN
D000818:Animals; D019204:GTP-Binding Proteins / Q000502:physiology*; D010727:Phosphoric Diester Hydrolases / Q000502:physiology; D015293:Transducin / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology*
D010727:Phosphoric Diester Hydrolases; D019204:GTP-Binding Proteins; D015293:Transducin