Laboratory of General Physiology, Department of Biological and Environmental Sciences and Technologies, University of Salento, I-73100 Lecce, Italy.
Proc Natl Acad Sci U S A. 2013 Apr 23;110(17):7068-73. doi: 10.1073/pnas.1220417110. Epub 2013 Apr 8.
Adaptation of organisms to extreme environments requires proteins to work at thermodynamically unfavorable conditions. To adapt to subzero temperatures, proteins increase the flexibility of parts of, or even the whole, 3D structure to compensate for the lower thermal kinetic energy available at low temperatures. This may be achieved through single-site amino acid substitutions in regions of the protein that undergo large movements during the catalytic cycle, such as in enzymes or transporter proteins. Other strategies of cold adaptation involving changes in the primary amino acid sequence have not been documented yet. In Antarctic icefish (Chionodraco hamatus) peptide transporter 1 (PEPT1), the first transporter cloned from a vertebrate living at subzero temperatures, we came upon a unique principle of cold adaptation. A de novo domain composed of one to six repeats of seven amino acids (VDMSRKS), placed as an extra stretch in the cytosolic COOH-terminal region, contributed per se to cold adaptation. VDMSRKS was in a protein region uninvolved in transport activity and, notably, when transferred to the COOH terminus of a warm-adapted (rabbit) PEPT1, it conferred cold adaptation to the receiving protein. Overall, we provide a paradigm for protein cold adaptation that relies on insertion of a unique domain that confers greater affinity and maximal transport rates at low temperatures. Due to its ability to transfer a thermal trait, the VDMSRKS domain represents a useful tool for future cell biology or biotechnological applications.
生物体对极端环境的适应需要蛋白质在热力学不利的条件下发挥作用。为了适应零下的温度，蛋白质会增加部分甚至整个 3D 结构的柔韧性，以弥补低温下较低的热动能。这可以通过在催化循环中发生较大运动的蛋白质区域中的单个氨基酸取代来实现，例如在酶或转运蛋白中。涉及一级氨基酸序列变化的其他寒冷适应策略尚未有记录。在南极冰鱼（Chionodraco hamatus）肽转运蛋白 1（PEPT1）中，我们发现了一种独特的寒冷适应原理。一个由一个到六个重复的七个氨基酸组成的新结构域（VDMSRKS），作为额外的伸展放置在胞质 COOH 末端区域，本身有助于寒冷适应。VDMSRKS 位于与转运活性无关的蛋白质区域中，特别是当它转移到温暖适应（兔子）PEPT1 的 COOH 末端时，它赋予了接收蛋白质对寒冷的适应能力。总的来说，我们提供了一个蛋白质寒冷适应的范例，该范例依赖于插入一个独特的结构域，该结构域在低温下赋予更高的亲和力和最大的转运速率。由于其能够传递热特性，VDMSRKS 结构域代表了未来细胞生物学或生物技术应用的有用工具。
