Close T J, Lammers P J
Department of Botany and Plant Sciences, University of California, Riverside 92521.
Plant Physiol. 1993 Mar;101(3):773-9. doi: 10.1104/pp.101.3.773.
Dehydrins are a family of desiccation proteins that were identified originally in plants (T.J. Close, A.A. Kortt, P.M. Chandler [1989] Plant Mol Biol 13: 95-108; G. Galau, T.J. Close [1992] Plant Physiol 98: 1523-1525). Dehydrins are characterized by the consensus amino acid sequence domain EKKGIMDKIKEKLPG found at or near the carboxy terminus; the core of this domain (KIKEKLPG) may be repeated from one to many times within the complete polypeptide. Dehydrins generally accumulate in plants in response to dehydration stress, regardless of whether the stimulus is evaporation, chilling, or a decrease in external osmotic potential. Polyclonal antibodies highly specific to the consensus carboxy terminus of plant dehydrins were used to search for dehydrins in cyanobacteria, many of which are known to survive desiccation. A 40-kD osmotic-stress-induced protein was identified in Anabaena sp. strain PCC 7120. The 40-kD protein was usually not detected in logarithmic cultures and was induced by shifting the growth medium to higher solute concentrations. Several solutes have inductive effects, including sucrose, sorbitol, and polyethylene glycol (PEG). Measurements of osmotic potential suggest that a shift of -0.5 MPa (sucrose and PEG) or -1.2 MPa (sorbitol) is sufficient to induce synthesis of the 40-kD protein. Glycerol, which is highly permeable, was not an inducer at -1.2 MPa (0.5 M), nor was the plant hormone abscisic acid. Induction appears to be evoked by a shift in osmotic potential approximately equal in absolute magnitude to the expected turgor pressure of bacterial cells in logarithmic phase growth. A dehydrin-like polypeptide was also identified among osmotically induced proteins from two other filamentous, heterocyst-forming cyano-bacteria. A 40-kD protein was observed in Calothrix sp. strain PCC 7601, and in Nostoc sp. strain Mac-R2, an osmotic-induced doublet at 39 and 40 kD was observed. From these data, it appears that cyanobacteria produce a dehydrin-like protein under osmotic stress.
脱水素是一类脱水蛋白，最初在植物中被鉴定出来（T.J. 克洛斯、A.A. 科特、P.M. 钱德勒 [1989] 《植物分子生物学》13: 95 - 108；G. 加劳、T.J. 克洛斯 [1992] 《植物生理学》98: 1523 - 1525）。脱水素的特征是在羧基末端或其附近存在一致的氨基酸序列结构域EKKGIMDKIKEKLPG；该结构域的核心（KIKEKLPG）在完整多肽中可能会重复一到多次。脱水素通常在植物中因脱水胁迫而积累，无论刺激是蒸发、低温还是外部渗透势降低。针对植物脱水素一致羧基末端具有高度特异性的多克隆抗体被用于在蓝细菌中寻找脱水素，其中许多蓝细菌已知能在干燥条件下存活。在鱼腥藻属PCC 7120菌株中鉴定出一种40-kD的渗透胁迫诱导蛋白。在对数生长期培养物中通常检测不到这种40-kD蛋白，通过将生长培养基转移到更高溶质浓度来诱导其产生。几种溶质具有诱导作用，包括蔗糖、山梨醇和聚乙二醇（PEG）。渗透势测量表明，-0.5 MPa（蔗糖和PEG）或-1.2 MPa（山梨醇）的变化足以诱导40-kD蛋白的合成。高渗透性的甘油在-1.2 MPa（0.5 M）时不是诱导剂，植物激素脱落酸也不是。诱导似乎是由渗透势的变化引起的，其绝对大小与对数期生长的细菌细胞预期的膨压大致相等。在另外两种丝状、形成异形胞的蓝细菌的渗透诱导蛋白中也鉴定出了一种脱水素样多肽。在眉藻属PCC 7601菌株中观察到一种40-kD蛋白，在念珠藻属Mac-R2菌株中观察到一种39和40 kD的渗透诱导双峰。从这些数据来看，似乎蓝细菌在渗透胁迫下会产生一种脱水素样蛋白。
