Ryan J C, Crouch R K, Ma J X
Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29403, USA.
Mol Vis. 2001 Oct 1;7:222-7.
Recent evidence has shown that the beta-gamma dimers (beta gamma) of activated heterotrimeric G-proteins are important in many cellular signaling pathways. Since two distinct transducin alpha subunits have been cloned from the salamander retina, we aimed to identify and characterize the G-protein beta (Gbeta) subunits that are involved in visual signal transduction in the salamander.
A salamander retina cDNA library was screened using degenerate oligonucleotide primers designed from a compilation of known Gbeta sequences. Tissue specific expression was determined by reverse transcriptase PCR (RT-PCR).
The library screening resulted in the cloning of three full-length sequences, two of which encode proteins of 340 residues and the third being an iniation variant of 353 and 395 residues. No identical matches were found in GenBank but each shows highest homology to G-beta-1 (beta1), G-beta-3 (beta3), and G-beta-5 (beta5 and beta5L) subunits of other species, respectively. The beta1 and beta3 subunits are 84.7% identical to each other but both show only 52% identity to beta5 at the protein level. RT-PCR analysis showed that all the subunits are expressed in multiple tissues, including the retina. However, the beta5L splice variant was found only in the retina.
Three distinct Gbeta subunit transcripts are expressed in the salamander retina. These subunits have proven to be important in the visual system of mammalian models.
最近的证据表明，活化的异源三聚体G蛋白的β-γ二聚体（βγ）在许多细胞信号通路中起着重要作用。由于已从蝾螈视网膜中克隆出两种不同的转导素α亚基，我们旨在鉴定和表征参与蝾螈视觉信号转导的G蛋白β（Gβ）亚基。
使用根据已知Gβ序列汇编设计的简并寡核苷酸引物筛选蝾螈视网膜cDNA文库。通过逆转录聚合酶链反应（RT-PCR）确定组织特异性表达。
文库筛选导致克隆出三个全长序列，其中两个编码340个残基的蛋白质，第三个是353和395个残基的起始变体。在GenBank中未发现完全匹配的序列，但每个序列分别与其他物种的G-β-1（β1）、G-β-3（β3）和G-β-5（β5和β5L）亚基显示出最高的同源性。β1和β3亚基彼此的同源性为84.7%，但在蛋白质水平上与β5的同源性仅为52%。RT-PCR分析表明，所有亚基均在包括视网膜在内的多种组织中表达。然而，β5L剪接变体仅在视网膜中发现。
蝾螈视网膜中表达三种不同的Gβ亚基转录本。这些亚基已被证明在哺乳动物模型的视觉系统中很重要。
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