Rosenquist M, Sehnke P, Ferl R J, Sommarin M, Larsson C
Department of Plant Biochemistry, Lund University, P.O. Box 117, SE-221 00 Lund, Sweden.
J Mol Evol. 2000 Nov;51(5):446-58. doi: 10.1007/s002390010107.
14-3-3 proteins constitute a family of eukaryotic proteins that are key regulators of a large number of processes ranging from mitosis to apoptosis. 14-3-3s function as dimers and bind to particular motifs in their target proteins. To date, 14-3-3s have been implicated in regulation or stabilization of more than 35 different proteins. This number is probably only a fraction of the number of proteins that 14-3-3s bind to, as reports of new target proteins have become more frequent. An examination of 14-3-3 entries in the public databases reveals 153 isoforms, including alleloforms, reported in 48 different species. The number of isoforms range from 2, in the unicellular organism Saccharomyces cerevisiae, to 12 in the multicellular organism Arabidopsis thaliana. A phylogenetic analysis reveals that there are four major evolutionary lineages: Viridiplantae (plants), Fungi, Alveolata, and Metazoa (animals). A close examination of the aligned amino acid sequences identifies conserved amino acid residues and regions of importance for monomer stabilization, dimer formation, target protein binding, and the nuclear export function. Given the fact that 53% of the protein is conserved, including all amino acid residues in the target binding groove of the 14-3-3 monomer, one might expect little to no isoform specificity for target protein binding. However, using surface plasmon resonance we show that there are large differences in affinity between nine 14-3-3 isoforms of A. thaliana and a target peptide representing a novel binding motif present in the C terminus of the plant plasma membrane H(+)ATPase. Thus, our data suggest that one reason for the large number of isoforms found in multicellular organisms is isoform-specific functions.
14-3-3蛋白构成了一个真核蛋白家族，是从有丝分裂到细胞凋亡等大量过程的关键调节因子。14-3-3蛋白以二聚体形式发挥作用，并与靶蛋白中的特定基序结合。迄今为止，14-3-3蛋白已被证明参与了35种以上不同蛋白的调节或稳定过程。随着新靶蛋白的报道越来越频繁，这个数字可能只是14-3-3蛋白所结合蛋白数量的一小部分。对公共数据库中14-3-3条目的检查显示，在48个不同物种中报道了153种亚型，包括等位亚型。亚型数量从单细胞生物酿酒酵母中的2种到多细胞生物拟南芥中的12种不等。系统发育分析表明，有四个主要的进化谱系：绿藻植物（植物）、真菌、囊泡虫和后生动物（动物）。对排列好的氨基酸序列进行仔细检查，可以确定保守的氨基酸残基以及对单体稳定、二聚体形成、靶蛋白结合和核输出功能重要的区域。鉴于53%的蛋白是保守的，包括14-3-3单体靶结合槽中的所有氨基酸残基，人们可能预计靶蛋白结合几乎没有亚型特异性。然而，我们使用表面等离子体共振表明，拟南芥的九种14-3-3亚型与代表植物质膜H(+)ATPase C末端新结合基序的靶肽之间的亲和力存在很大差异。因此，我们的数据表明，在多细胞生物中发现大量亚型的一个原因是亚型特异性功能。
