Li N, Fariss R N, Zhang K, Otto-Bruc A, Haeseleer F, Bronson D, Qin N, Yamazaki A, Subbaraya I, Milam A H, Palczewski K, Baehr W
Moran Eye Center, University of Utah Health Science Center, Salt Lake City 84132, USA.
Eur J Biochem. 1998 Mar 15;252(3):591-9. doi: 10.1046/j.1432-1327.1998.2520591.x.
Two guanylate-cyclase-activating proteins (GCAP) encoded by a tail-to-tail gene array have been characterized in the mammalian retina. Using frog retina as a model, we obtained evidence for the presence of a photoreceptor Ca2+-binding protein closely related to GCAP. This protein (206 amino acids) does not stimulate guanylate cyclase (GC) in low [Ca2+], but inhibits GC in high [Ca2+], and is therefore termed guanylate-cyclase-inhibitory protein (GCIP). Sequence analysis indicates that GCIP and GCAP1 and GCAP2 have diverged substantially, but conserved domains present in all vertebrate GCAP are present in GCIP. Moreover, partial characterization of the GCIP gene showed that the positions of two introns in the GCIP gene are identical to positions of corresponding introns of the mammalian GCAP gene array. As to the major differences between GCIP and GCAP, the fourth EF hand Ca2+-binding motif of GCIP is disabled for Ca2+ binding, and GCIP does not stimulate GC. Monoclonal and polyclonal antibodies raised against recombinant GCIP identified high levels of GCIP in the inner segments, somata and synaptic terminals of frog cone photoreceptors. The results suggest that GCIP is a Ca2+-binding protein of the GCAP/recoverin subfamily. Its localization in frog cones closely resembles that of GC in mammalian cones. GCIP inhibits GC at high free [Ca2+], competing with GCAP1 and GCAP2 for GC regulatory sites.
由一个尾对尾基因阵列编码的两种鸟苷酸环化酶激活蛋白（GCAP）已在哺乳动物视网膜中得到表征。以蛙视网膜为模型，我们获得了与GCAP密切相关的光感受器钙结合蛋白存在的证据。这种蛋白（206个氨基酸）在低[Ca2+]浓度下不刺激鸟苷酸环化酶（GC），但在高[Ca2+]浓度下抑制GC，因此被称为鸟苷酸环化酶抑制蛋白（GCIP）。序列分析表明，GCIP与GCAP1和GCAP2有很大差异，但所有脊椎动物GCAP中存在的保守结构域在GCIP中也存在。此外，GCIP基因的部分特征表明，GCIP基因中两个内含子的位置与哺乳动物GCAP基因阵列中相应内含子的位置相同。至于GCIP和GCAP之间的主要差异，GCIP的第四个EF手型钙结合基序丧失了钙结合能力，且GCIP不刺激GC。针对重组GCIP产生的单克隆抗体和多克隆抗体在蛙视锥光感受器的内段、胞体和突触终末中检测到高水平的GCIP。结果表明，GCIP是GCAP/恢复蛋白亚家族的一种钙结合蛋白。它在蛙视锥中的定位与哺乳动物视锥中GC的定位非常相似。GCIP在高游离[Ca2+]浓度下抑制GC，与GCAP1和GCAP2竞争GC调节位点。
