Rorat Tadeusz
Institute of Plant Genetics, PAS, Poznań, Poland.
Cell Mol Biol Lett. 2006;11(4):536-56. doi: 10.2478/s11658-006-0044-0. Epub 2006 Sep 14.
Dehydrins (DHNs) are part of a large group of highly hydrophilic proteins known as LEA (Late Embryogenesis Abundant). They were originally identified as group II of the LEA proteins. The distinctive feature of all DHNs is a conserved, lysine-rich 15-amino acid domain, EKKGIMDKIKEKLPG, named the K-segment. It is usually present near the C-terminus. Other typical dehydrin features are: a track of Ser residues (the S-segment); a consensus motif, T/VDEYGNP (the Y-segment), located near the N-terminus; and less conserved regions, usually rich in polar amino acids (the Phi-segments). They do not display a well-defined secondary structure. The number and order of the Y-, S-and K-segments define different DHN sub-classes: Y(n)SK(n), Y(n)Kn, SK(n), K(n) and K(n)S. Dehydrins are distributed in a wide range of organisms including the higher plants, algae, yeast and cyanobacteria. They accumulate late in embryogenesis, and in nearly all the vegetative tissues during normal growth conditions and in response to stress leading to cellular dehydration (e.g. drought, low temperature and salinity). DHNs are localized in different cell compartments, such as the cytosol, nucleus, mitochondria, vacuole, and the vicinity of the plasma membrane; however, they are primarily localized to the cytoplasm and nucleus. The precise function of dehydrins has not been established yet, but in vitro experiments revealed that some DHNs (YSK(n)-type) bind to lipid vesicles that contain acidic phospholipids, and others (K(n)S) were shown to bind metals and have the ability to scavenge hydroxyl radicals [Asghar, R. et al. Protoplasma 177 (1994) 87-94], protect lipid membranes against peroxidation or display cryoprotective activity towards freezing-sensitive enzymes. The SK(n)-and K-type seem to be directly involved in cold acclimation processes. The main question arising from the in vitro findings is whether each DHN structural type could possess a specific function and tissue distribution. Much recent in vitro data clearly indicates that dehydrins belonging to different subclasses exhibit distinct functions.
脱水素(DHNs)是一大类被称为胚胎后期丰富蛋白(LEA)的高度亲水性蛋白质的一部分。它们最初被鉴定为LEA蛋白的第二组。所有脱水素的显著特征是一个保守的、富含赖氨酸的15个氨基酸的结构域,即EKKGIMDKIKEKLPG,称为K片段。它通常位于C末端附近。其他典型的脱水素特征包括:一串丝氨酸残基(S片段);一个共有基序T/VDEYGNP(Y片段),位于N末端附近;以及通常富含极性氨基酸的保守性较低的区域(φ片段)。它们不具有明确的二级结构。Y、S和K片段的数量和顺序定义了不同的脱水素亚类:Y(n)SK(n)、Y(n)Kn、SK(n)、K(n)和K(n)S。脱水素分布于广泛的生物体中,包括高等植物、藻类、酵母和蓝细菌。它们在胚胎发育后期积累,并且在正常生长条件下以及响应导致细胞脱水的胁迫(如干旱、低温和盐度)时,几乎在所有营养组织中都会积累。脱水素定位于不同的细胞区室,如细胞质、细胞核、线粒体、液泡和质膜附近;然而,它们主要定位于细胞质和细胞核。脱水素的确切功能尚未确定,但体外实验表明,一些脱水素(YSK(n)型)与含有酸性磷脂的脂质囊泡结合,而其他脱水素(K(n)S)则被证明能结合金属并具有清除羟自由基的能力[阿斯加尔,R.等人。原生质体177 (1994) 87 - 94],保护脂质膜免受过氧化作用,或对冷冻敏感的酶表现出冷冻保护活性。SK(n)型和K型似乎直接参与冷驯化过程。体外研究结果引发的主要问题是,每种脱水素结构类型是否可能具有特定的功能和组织分布。最近的许多体外数据清楚地表明,属于不同亚类的脱水素表现出不同的功能。