Abstract
Purpose: :
To investigate the role of the rod cell specific transducin beta-gamma subunit complex in ROS membrane partitioning and translocation properties of rod transducin alpha.
Methods: :
GNGT(-/-) mice lacking rod transducin beta-gamma subunit complex were used in this study. Sub-cellular distribution of transducin alpha was examined by immunohistochemistry under various light intensity conditions. Light- and nucleotide-dependent ROS membrane partitioning was studied using purified mouse ROS and quantitative immunoblotting.
Results: :
Significant amount of transducin alpha is found in GNGT(-/-) mouse ROS in the dark as determined by immunofluorescence analysis of retina sections, but the affinity of transducin alpha towards rhodopsin-containing ROS membranes is reduced in the absence of transducin beta-gamma complex. Light-activation further decreases ROS membrane partitioning and is accompanied by translocation of transducin alpha to RIS. In purified GNGT(-/-) mouse ROS transducin alpha binds to the light activated rhodopsin in a nucleotide-dependent manner, but the ROS membrane affinity is decreases.
Conclusions: :
Rod transducin beta-gamma complex is responsible for proper partitioning of transducin heterotrimer to ROS membranes and determines the affinity of transducin alpha towards rhodopsin.Financial support: NIH grant RO1GM63203, R21EY018107, RPB (OGK)
Keywords: photoreceptors • protein structure/function • retina