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STRUCTURAL PROPERTIES AND ROLE IN PHOTOTRANSDUCTION

Molday, Robert S. and Hsu, Yi-Te (1995) STRUCTURAL PROPERTIES AND ROLE IN PHOTOTRANSDUCTION.

Short Abstract:

The cGMP-gated channel responds to changes in free intracellular cGMP. As a result, it plays a central role in the phototransduction process in rod and cone photoreceptor cells. Recent biochemical, immunochemical and molecular biology studies indicate that this channel consists of a complex of two distinct subunits and one or more associated proteins. Primary structural analysis indicates that the * and * subunits contain a cGMP-binding domain, an even number of membrane spanning segments, a voltage sensor motif and a pore region. The latter two features are found in voltage-gated channels and suggest that these two classes of channels have evolved from the same ancestral channel protein. A working model for the membrane topography of the channel subunits is proposed based on immunogold labeling studies and sequence analysis. Recent studies also indicate that calmodulin binds to the 240 kDa protein of the channel complex and modulates the sensitivity of the channel for cGMP in a Ca2+ dependent manner. The molecular properties of the channel complex and the possible role of Ca2+-calmodulin modulation of the channel during photoactivation and photorecovery is discussed in relation to the current mechanism of phototransduction in photoreceptor cells.

Long Abstract:

The cGMP-gated channel responds to changes in free intracellular cGMP. As a result, it plays a central role in the phototransduction process in rod and cone photoreceptor cells. Recent biochemical, immunochemical and molecular biology studies indicate that this channel consists of a complex of two distinct subunits and one or more associated proteins. Primary structural analysis indicates that the * and * subunits contain a cGMP-binding domain, an even number of membrane spanning segments, a voltage sensor motif and a pore region. The latter two features are found in voltage-gated channels and suggest that these two classes of channels have evolved from the same ancestral channel protein. A working model for the membrane topography of the channel subunits is proposed based on immunogold labeling studies and sequence analysis. Recent studies also indicate that calmodulin binds to the 240 kDa protein of the channel complex and modulates the sensitivity of the channel for cGMP in a Ca2+ dependent manner. The molecular properties of the channel complex and the possible role of Ca2+-calmodulin modulation of the channel during photoactivation and photorecovery is discussed in relation to the current mechanism of phototransduction in photoreceptor cells.

Keywords:	Rod photoreceptor cells, phototransduction; photorecovery; cGMP-gated channel, calmodulin
Subjects:	BBS Special Issues: Controversies in Neuroscience: III - Signal Transduction in the Retina and Brain Psychology: Cognitive Psychology Neuroscience: Neuroanatomy Neuroscience: Neurochemistry Neuroscience: Neuroendocrinology Neuroscience: Neural Modelling Neuroscience: Neurology Neuroscience: Neurophysiology Neuroscience: Neuropsychology
ID code:	bbs00000517
Deposited by:	Robert Molday on 02 May 2001