Plant Biophysics, Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid Madrid, Spain.
Front Plant Sci. 2012 Nov 29;3:263. doi: 10.3389/fpls.2012.00263. eCollection 2012.
Electrophysiological analyses conducted about 25 years ago detected two types of anion channels in the plasma membrane of guard cells. One type of channel responds slowly to changes in membrane voltage while the other responds quickly. Consequently, they were named SLAC, for SLow Anion Channel, and QUAC, for QUick Anion Channel. Recently, genes SLAC1 and QUAC1/ALMT12, underlying the two different anion current components, could be identified in the model plant Arabidopsis thaliana. Expression of the gene products in Xenopus oocytes confirmed the quick and slow current kinetics. In this study we provide an overview on our current knowledge on slow and quick anion channels in plants and analyze the molecular evolution of ALMT/QUAC-like and SLAC-like channels. We discovered fingerprints that allow screening databases for these channel types and were able to identify 192 (177 non-redundant) SLAC-like and 422 (402 non-redundant) ALMT/QUAC-like proteins in the fully sequenced genomes of 32 plant species. Phylogenetic analyses provided new insights into the molecular evolution of these channel types. We also combined sequence alignment and clustering with predictions of protein features, leading to the identification of known conserved phosphorylation sites in SLAC1-like channels along with potential sites that have not been yet experimentally confirmed. Using a similar strategy to analyze the hydropathicity of ALMT/QUAC-like channels, we propose a modified topology with additional transmembrane regions that integrates structure and function of these membrane proteins. Our results suggest that cross-referencing phylogenetic analyses with position-specific protein properties and functional data could be a very powerful tool for genome research approaches in general.
大约 25 年前进行的电生理分析检测到质膜保卫细胞中有两种阴离子通道。一种类型的通道对膜电压的变化反应缓慢，而另一种类型的通道反应迅速。因此，它们被命名为 SLAC，代表 SLow Anion Channel，QUAC，代表 QUick Anion Channel。最近，在模式植物拟南芥中可以鉴定出两种不同阴离子电流成分的 SLAC1 和 QUAC1/ALMT12 基因。在非洲爪蟾卵母细胞中表达基因产物证实了快速和缓慢电流动力学。在这项研究中，我们提供了植物中慢和快阴离子通道的最新知识概述，并分析了 ALMT/QUAC 样和 SLAC 样通道的分子进化。我们发现了指纹，可以筛选数据库以鉴定这些通道类型，并能够在 32 种完全测序的植物基因组中鉴定出 192 个（177 个非冗余）SLAC 样和 422 个（402 个非冗余）ALMT/QUAC 样蛋白。系统发育分析提供了这些通道类型分子进化的新见解。我们还将序列比对和聚类与蛋白质特征预测相结合，确定了 SLAC1 样通道中已知的保守磷酸化位点以及尚未通过实验证实的潜在位点。使用类似的策略来分析 ALMT/QUAC 样通道的疏水性，我们提出了一种具有额外跨膜区域的改良拓扑结构，该结构整合了这些膜蛋白的结构和功能。我们的结果表明，将系统发育分析与位置特异性蛋白质特性和功能数据交叉引用可能是一般基因组研究方法的非常强大的工具。
