Ca(2+)-binding proteins in the retina: structure, function, and the etiology of human visual diseases.
The complex sensation of vision begins with the relatively simple photoisomerization of the visual pigment chromophore 11-cis-retinal to its all-trans configuration. This event initiates a series of biochemical reactions that are collectively referred to as phototransduction, which ultimately lead to a change in the electrochemical signaling of the photoreceptor cell. To operate in a wide range of light intensities, however, the phototransduction pathway must allow for adjustments to background light. These take place through physiological adaptation processes that rely primarily on Ca(2+) ions. While Ca(2+) may modulate some activities directly, it is more often the case that Ca(2+)-binding proteins mediate between transient changes in the concentration of Ca(2+) and the adaptation processes that are associated with phototransduction. Recently, combined genetic, physiological, and biochemical analyses have yielded new insights about the properties and functions of many phototransduction-specific components, including some novel Ca(2+)-binding proteins. Understanding these Ca(2+)-binding proteins will provide a more complete picture of visual transduction, including the mechanisms associated with adaptation, and of related degenerative diseases.
Palczewski
K
K
Department of Ophthalmology, University of Washington, Seattle, WA 98195-6485, USA. palczews@u.washington.edu
Polans
A S
AS
Baehr
W
W
Ames
J B
JB
D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005128:Eye Diseases / Q000209:etiology*; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism; D051604:Guanylate Cyclase-Activating Proteins; D006801:Humans; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism; D011487:Protein Conformation; D012160:Retina / Q000378:metabolism*
D002135:Calcium-Binding Proteins; C496736:GUCA1A protein, human; C496739:GUCA1B protein, human; D051604:Guanylate Cyclase-Activating Proteins; D006162:Guanylate Cyclase