Accessibilities of N-terminal myristoyl chain and cysteines in guanylyl cyclase-activating protein-2 (GCAP-2) studied by covalent labeling and mass spectrometry

摘要

The guanylyl cyclase-activating protein 2 (GCAP-2) has been identified in mammalian photoreceptor cells where it controls retinal rod-outer-segment guanylyl cyclase (ROS-GC) activity in a Ca~(2+)-dependent manner.~([1-4]) ROS-GCs convert GTP into cGMP-the second messenger involved in photo-transduction. Their GCAP-mediated Ca~(2+)-dependent regulation plays a central role in light adaptation and in modulating the photoreceptor light response.~([5]) GCAP-2 belongs to the neuronal calcium sensor family and is myristoylated at its N-terminus.~([6]) The three-dimensional structure of GCAP-2 has so far only been determined for non-myristoylated Ca~(2+)-loaded protein.~([7]) In previous studies, it was concluded that the lack of myristoylation does not significantly affect the ability of GCAP-2 to stimulate ROS-GC[6] and that the myristoyl group controls the Ca~(2+) sensitivity of GCAP-1, but not that of GCAP-2.~([8])