CALCIUM-MODULATED SIGNALING SITE IN TYPE-2 ROD OUTER SEGMENT MEMBRANEGUANYLATE-CYCLASE (ROS-GC2)

The ROS-GC subfamily of membrane guanylate cyclases is at present repr esented by two members: ROS-GC1 and ROS-GC2. A unique functional featu re of this subfamily is that it is intracellularly modulated in low Ca 2+ concentration by calmodulin-like Ca2+-binding proteins termed GCAPs , 1 and 2, and the modulation is consistent with its linkage to photot ransduction. The present study shows that: (1) GCAP2 is a specific mod ulator of ROS-GC2; (2) through systematic remodeling of ROS-GC modules , the study also shows that the modulated domain resides within the am ino acid segment 736-1020. This domain is distinct form the correspond ing GCAP1-modulated ROS-GC1 domain, Thus, GCAP1 and GCAP2 act through different ROS-GCs and through two different cyclase domains. (C) 1998 Academic Press.