Langdon G M, Jiménez M A, Genzor C G, Maldonado S, Sancho J, Rico M
Instituto de Estructura de la Materia, C.S.I.C., Madrid, Spain.
Proteins. 2001 Jun 1;43(4):476-88. doi: 10.1002/prot.1059.
An important issue in modern protein biophysics is whether structurally homologous proteins share common stability and/or folding features. Flavodoxin is an archetypal alpha/beta protein organized in three layers: a central beta-sheet (strand order 21345) flanked by helices 1 and 5 on one side and helices 2, 3, and 4 on the opposite side. The backbone internal dynamics of the apoflavodoxin from Anabaena is analyzed here by the hydrogen exchange method. The hydrogen exchange rates indicate that 46 amide protons, distributed throughout the structure of apoflavodoxin, exchange relatively slowly at pH 7.0 (k(ex) < 10(-1) min(-1)). According to their distribution in the structure, protein stability is highest on the beta-sheet, helix 4, and on the layer formed by helices 1 and 5. The exchange kinetics of Anabaena apoflavodoxin was compared with those of the apoflavodoxin from Azotobacter, with which it shares a 48% sequence identity, and with Che Y and cutinase, two other alpha/beta (21345) proteins with no significant sequence homology with flavodoxins. Both similarities and differences are observed in the cores of these proteins. It is of interest that a cluster of a few structurally equivalent residues in the central beta-strands and in helix 5 is common to the cores.
现代蛋白质生物物理学中的一个重要问题是，结构同源的蛋白质是否具有共同的稳定性和/或折叠特征。黄素氧还蛋白是一种典型的α/β蛋白，由三层组成：中间的β-折叠（链序为21345），一侧由螺旋1和螺旋5环绕，另一侧由螺旋2、螺旋3和螺旋4环绕。本文采用氢交换法分析了鱼腥藻脱辅基黄素氧还蛋白的主链内部动力学。氢交换速率表明，在pH 7.0时，分布在脱辅基黄素氧还蛋白整个结构中的46个酰胺质子交换相对较慢（k(ex) < 10(-1) min(-1)）。根据它们在结构中的分布，蛋白质稳定性在β-折叠、螺旋4以及由螺旋1和螺旋5形成的层上最高。将鱼腥藻脱辅基黄素氧还蛋白的交换动力学与固氮菌黄素氧还蛋白（与之具有48%的序列同一性）以及Che Y和角质酶（另外两种与黄素氧还蛋白无显著序列同源性的α/β(21345)蛋白）的交换动力学进行了比较。在这些蛋白质的核心区域观察到了相似性和差异。有趣的是，核心区域中一些结构等效的残基簇在中间β-链和螺旋5中是共有的。
