Lee Chang-Hun, Jung Jin-Won, Yee Adelinda, Arrowsmith Cheryl H, Lee Weontae
Department of Biochemistry, College of Science, Yonsei University, 134 Seodaemoon-Gu, Shinchondong, Seoul, Korea 120-749.
Protein Sci. 2004 Apr;13(4):1148-54. doi: 10.1110/ps.03472104.
MTH1880 is a hypothetical protein from Methanobacterium thermoautotrophicum, a target organism of structural genomics. The solution structure determined by NMR spectroscopy demonstrates a typical alpha + beta-fold found in many proteins with different functions. The molecular surface of the protein reveals a small, highly acidic pocket comprising loop B (Asp36, Asp37, Asp38), the end of beta2 (Glu39), and loop D (Ser57, Ser58, Ser61), indicating that the protein would have a possible cation binding site. The NMR resonances of several amino acids within the acidic binding pocket in MTH1880, shifted upon addition of calcium ion. This calcium binding motif and overall topology of MTH1880 differ from those of other calcium binding proteins. MTH1880 did not show a calcium-induced conformational change typical of calcium sensor proteins. Therefore, we propose that the MTH1880 protein contains a novel motif for calcium-specific binding, and may function as a calcium buffering protein.
MTH1880是来自嗜热自养甲烷杆菌的一种假设蛋白，嗜热自养甲烷杆菌是结构基因组学的一个目标生物体。通过核磁共振光谱法确定的溶液结构显示出在许多具有不同功能的蛋白质中发现的典型α + β折叠。该蛋白质的分子表面显示出一个小的、高度酸性的口袋，它由环B（天冬氨酸36、天冬氨酸37、天冬氨酸38）、β2的末端（谷氨酸39）和环D（丝氨酸57、丝氨酸58、丝氨酸61）组成，这表明该蛋白质可能有一个阳离子结合位点。在添加钙离子后，MTH1880中酸性结合口袋内几个氨基酸的核磁共振共振发生了位移。MTH1880的这种钙结合基序和整体拓扑结构与其他钙结合蛋白不同。MTH1880没有表现出钙传感器蛋白典型的钙诱导构象变化。因此，我们提出MTH1880蛋白含有一种用于钙特异性结合的新基序，并且可能作为一种钙缓冲蛋白发挥作用。
