Hara Masakazu, Endo Takuya, Kamiya Keita, Kameyama Ayuko
Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan.
J Plant Physiol. 2017 Mar;210:18-23. doi: 10.1016/j.jplph.2016.12.003. Epub 2016 Dec 14.
Dehydrins, which are group 2 late embryogenesis abundant (LEA) proteins, accumulate in plants during the development of the embryo and exposure to abiotic stresses including low temperature. Dehydrins exhibit cryoprotection of freezing-sensitive enzymes, e.g. lactate dehydrogenase (LDH). Although it has been reported that K-segments conserved in dehydrins are related to their cryoprotection activity, it has not been determined which sequence features of the K-segments contribute to the cryoprotection. A cryoprotection assay using LDH indicated that 13 K-segments including 12 K-segments found in Arabidopsis dehydrins and a typical K-segment (TypK, EKKGIMEKIKEKLPG) derived from the K-segments of many plants showed similar cryoprotective activities. Mutation of the TypK sequence demonstrated that hydrophobic amino acids were clearly involved in preventing the cryoinactivation, cryoaggregation, and cryodenaturation of LDH. We propose that the cryoprotective activities of dehydrins may be made possible by the hydrophobic residues of the K-segments.
脱水素是第2组胚胎发育晚期丰富（LEA）蛋白，在胚胎发育过程中以及暴露于包括低温在内的非生物胁迫时在植物中积累。脱水素对冷冻敏感的酶具有冷冻保护作用，例如乳酸脱氢酶（LDH）。虽然已有报道称脱水素中保守的K片段与其冷冻保护活性有关，但尚未确定K片段的哪些序列特征有助于冷冻保护。使用LDH进行的冷冻保护试验表明，13个K片段，包括在拟南芥脱水素中发现的12个K片段以及源自许多植物K片段的典型K片段（TypK，EKKGIMEKIKEKLPG），表现出相似的冷冻保护活性。TypK序列的突变表明，疏水氨基酸明显参与防止LDH的冷冻失活、冷冻聚集和冷冻变性。我们提出，脱水素的冷冻保护活性可能是由K片段的疏水残基实现的。
