Malik Ahmad A, Veltri Michael, Boddington Kelly F, Singh Karamjeet K, Graether Steffen P
Department of Molecular and Cellular Biology, University of Guelph, GuelphON, Canada.
Front Plant Sci. 2017 May 4;8:709. doi: 10.3389/fpls.2017.00709. eCollection 2017.
Dehydrins, a large family of abiotic stress proteins, are defined by the presence of a mostly conserved motif known as the K-segment, and may also contain two other conserved motifs known as the Y-segment and S-segment. Using the dehydrin literature, we developed a sequence motif definition of the K-segment, which we used to create a large dataset of dehydrin sequences by searching the Pfam00257 dehydrin dataset and the Phytozome 10 sequences of vascular plants. A comprehensive analysis of these sequences reveals that lysine residues are highly conserved in the K-segment, while the amino acid type is often conserved at other positions. Despite the Y-segment name, the central tyrosine is somewhat conserved, but can be substituted with two other small aromatic amino acids (phenylalanine or histidine). The S-segment contains a series of serine residues, but in some proteins is also preceded by a conserved LHR sequence. In many dehydrins containing all three of these motifs the S-segment is linked to the K-segment by a GXGGRRKK motif (where X can be any amino acid), suggesting a functional linkage between these two motifs. An analysis of the sequences shows that the dehydrin architecture and several biochemical properties (isoelectric point, molecular mass, and hydrophobicity score) are dependent on each other, and that some dehydrin architectures are overexpressed during certain abiotic stress, suggesting that they may be optimized for a specific abiotic stress while others are involved in all forms of dehydration stress (drought, cold, and salinity).
脱水素是一类非生物胁迫蛋白大家族，其定义特征是存在一个大多保守的基序，即K片段，并且可能还包含另外两个保守基序，即Y片段和S片段。利用脱水素相关文献，我们制定了K片段的序列基序定义，并通过搜索Pfam00257脱水素数据集和维管植物的植物基因组10序列，创建了一个大型脱水素序列数据集。对这些序列的全面分析表明，赖氨酸残基在K片段中高度保守，而其他位置的氨基酸类型通常也保守。尽管名为Y片段，但其中央酪氨酸仅稍有保守，不过可被另外两种小的芳香族氨基酸（苯丙氨酸或组氨酸）取代。S片段包含一系列丝氨酸残基，但在某些蛋白质中其前面还有一个保守的LHR序列。在许多含有所有这三个基序的脱水素中，S片段通过一个GXGGRRKK基序（其中X可以是任何氨基酸）与K片段相连，这表明这两个基序之间存在功能联系。序列分析表明，脱水素结构与若干生化特性（等电点、分子量和疏水评分）相互依赖，并且某些脱水素结构在特定非生物胁迫期间过表达，表示它们可能针对特定非生物胁迫进行了优化，而其他脱水素则参与所有形式的脱水胁迫（干旱、寒冷和盐胁迫）。
