Balakrishnan R, Ramasubbu N, Varughese K I, Parthasarathy R
Biophysics Department and Center for Crystallographic Research, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
Proc Natl Acad Sci U S A. 1997 Sep 2;94(18):9620-5. doi: 10.1073/pnas.94.18.9620.
We report the crystal structures of the copper and nickel complexes of RNase A. The overall topology of these two complexes is similar to that of other RNase A structures. However, there are significant differences in the mode of binding of copper and nickel. There are two copper ions per molecule of the protein, but there is only one nickel ion per molecule of the protein. Significant changes occur in the interprotein interactions as a result of differences in the coordinating groups at the common binding site around His-105. Consequently, the copper- and nickel-ion-bound dimers of RNase A act as nucleation sites for generating different crystal lattices for the two complexes. A second copper ion is present at an active site residue His-119 for which all the ligands are from one molecule of the protein. At this second site, His-119 adopts an inactive conformation (B) induced by the copper. We have identified a novel copper binding motif involving the alpha-amino group and the N-terminal residues.
我们报道了核糖核酸酶A的铜和镍配合物的晶体结构。这两种配合物的整体拓扑结构与其他核糖核酸酶A结构相似。然而，铜和镍的结合模式存在显著差异。每个蛋白质分子中有两个铜离子，但每个蛋白质分子中只有一个镍离子。由于围绕组氨酸-105的共同结合位点处配位基团的差异，蛋白质间相互作用发生了显著变化。因此，核糖核酸酶A的铜离子和镍离子结合二聚体作为成核位点，为这两种配合物生成不同的晶格。第二个铜离子存在于活性位点残基组氨酸-119处，其所有配体均来自一个蛋白质分子。在这个第二个位点，组氨酸-119采用由铜诱导的无活性构象（B）。我们鉴定出了一种涉及α-氨基和N端残基的新型铜结合基序。
