Munger S D, Schremser-Berlin J L, Brink C M, Battelle B A
Whitney Laboratory, University of Florida, St. Augustine 32086, USA.
Invert Neurosci. 1996 Dec;2(3):175-82. doi: 10.1007/BF02214173.
GTP binding proteins of the Gq family have been implicated in phototransduction in rhabdomeral photoreceptors. In this study we used molecular and immunochemical techniques to characterize a GTP-binding protein alpha subunit of the Gq family in ventral and lateral photoreceptors of the horseshoe crab, Limulus polyphemus. Both ventral photoreceptors and lateral eye retinular cells became strongly labeled with an antibody directed against the common carboxyl tail of two Gq family proteins, G alpha q and G alpha 11. This antibody also labeled a 42 kDa band on Western blots of proteins from ventral photoreceptor cell bodies, ventral photoreceptor axons, lateral eyes and lateral optic nerves. The reverse transcription-polymerase chain reaction (RT-PCR), along with degenerate oligonucleotide primers designed against conserved regions of known G alpha q and G alpha 11 proteins, was used to isolate a cDNA from ventral eye RNA which encodes a protein with high identity to known Gq proteins. Ribonuclease protection assays showed that the corresponding message was expressed in ventral eye, but these assays, as well as Northern blots, failed to detect expression in lateral eye. Therefore, while photoreceptors of both ventral and lateral eyes contain a Gq-like protein, the mRNA encoding the Gq protein in the ventral eye may differ in nucleotide sequence from its lateral eye counterpart.
Gq家族的GTP结合蛋白已被认为参与了复眼小网膜感光细胞的光转导过程。在本研究中，我们运用分子和免疫化学技术，对美洲鲎（Limulus polyphemus）腹侧和外侧感光细胞中Gq家族的一种GTP结合蛋白α亚基进行了表征。针对Gq家族的两种蛋白Gαq和Gα11的共同羧基末端的抗体，使腹侧感光细胞和侧眼视小网膜细胞均被强烈标记。该抗体在来自腹侧感光细胞胞体、腹侧感光细胞轴突、侧眼和外侧视神经的蛋白质的蛋白质印迹上，也标记出了一条42 kDa的条带。利用逆转录-聚合酶链反应（RT-PCR），以及针对已知Gαq和Gα11蛋白保守区域设计的简并寡核苷酸引物，从腹侧眼RNA中分离出了一个cDNA，其编码的蛋白质与已知Gq蛋白具有高度同源性。核糖核酸酶保护分析表明相应的信息在腹侧眼中表达，但这些分析以及Northern印迹均未能检测到在侧眼中的表达。因此，虽然腹侧眼和侧眼的感光细胞都含有一种Gq样蛋白，但腹侧眼中编码Gq蛋白的mRNA在核苷酸序列上可能与其在侧眼中的对应物不同。
