Marino M, Galvano M, Cambria A, Polticelli F, Desideri A
Institute of Biochemical and Pharmacological Sciences, University of Catania, Italy.
Protein Eng. 1995 Jun;8(6):551-6. doi: 10.1093/protein/8.6.551.
The three-dimensional structure of tomato P31 and T10 Cu,Zn superoxide dismutases (SODs) were computer modelled using the structure of the bovine enzyme as a template. The structure-essential residues retain in the models the position occupied in the other Cu,Zn SODs of known 3D structure and the overall packing of the beta-barrel is maintained. Formation of 'aromatic pairs' occurs between newly inserted aromatic residues. The number of total charges changes in the two variants and some charged residues located in the proximity of the active site in most Cu,Zn SODs disappear in tomato enzymes. Calculation of the electrostatic potential field, carried out by numerically solving the Poisson-Boltzmann equation, indicates that in both variants a negative potential field surrounds all the protein surface except the active site areas, characterized by positive potential values, as already observed in the bovine enzyme. This result confirms that coordinated mutations of charged residues have occurred in the evolution of this enzyme giving rise to a peculiar electrostatic potential distribution common to all members of this protein family.
利用牛酶的结构作为模板，对番茄P31和T10铜锌超氧化物歧化酶（SOD）的三维结构进行了计算机建模。结构必需残基在模型中保留了在已知三维结构的其他铜锌SOD中占据的位置，并且β桶的整体堆积得以维持。新插入的芳香族残基之间会形成“芳香对”。这两个变体中的总电荷数发生了变化，并且大多数铜锌SOD中位于活性位点附近的一些带电残基在番茄酶中消失了。通过数值求解泊松-玻尔兹曼方程进行的静电势场计算表明，在这两个变体中，除了活性位点区域外，所有蛋白质表面都被负电势场包围，活性位点区域的特征是正电势值，这与在牛酶中观察到的情况一致。该结果证实，在这种酶的进化过程中发生了带电残基的协同突变，从而产生了该蛋白质家族所有成员共有的特殊静电势分布。
