STRUCTURAL AND FUNCTIONAL-CHARACTERIZATION OF A 2ND SUBFAMILY MEMBER OF THE CALCIUM-MODULATED BOVINE ROD OUTER SEGMENT MEMBRANE GUANYLATE-CYCLASE, ROS-GC2

A native bovine calcium-modulated rod outer segment membrane guanylate cyclase (ROS GC) has been cloned and reconstituted to show its linkag e consistent to the process of phototransduction. In the present study , a second form of the membrane guanylate cyclase has been cloned from the bovine retina. This cyclase shares a high sequence identity with ROS-GC, is specifically expressed in the bovine retina, and, like ROS- GC, is modulated in low Ca2+ by a calmodulin-like Ca2+-binding protein , termed GCAP2. For this reason, this cyclase has now been named ROS-G C2 and the previously described ROS-GC as ROS-GC1. The tail end of ROS -GC2 contains a stretch of five amino acids, a structural feature uniq ue to itself. These findings support the existence of a calcium-modula ted subfamily of ROS-GC and indicate that ROS-GC2 embodies a five amin o acid signature element at its tail end. (C) 1997 Academic Press.