Bagby S, Harvey T S, Eagle S G, Inouye S, Ikura M
Division of Molecular and Structural Biology, Ontario Cancer Institute, University of Toronto, Canada.
Proc Natl Acad Sci U S A. 1994 May 10;91(10):4308-12. doi: 10.1073/pnas.91.10.4308.
The solution structure of Ca(2+)-loaded protein S (M(r) 18,792) from the Gram-negative soil bacterium Myxococcus xanthus has been determined by multidimensional heteronuclear NMR spectroscopy. Protein S consists of four internally homologous motifs, arranged to produce two domains with a pseudo-twofold symmetry axis, overall resembling a triangular prism. Each domain consists of two topologically inequivalent "Greek keys": the second and fourth motifs form standard Greek keys, whereas the first and third motifs each contain a regular alpha-helix in addition to the usual four beta-strands. The structure of protein S is similar to those of the vertebrate eye lens beta gamma-crystallins, which are thought to be evolutionarily related to protein S. Both protein S and the beta gamma-crystallins function by forming stable multimolecular assemblies. However, protein S possesses distinctive motif organization and domain packing, indicating a different mode of oligomerization and a divergent evolutionary pathway from the beta gamma-crystallins.
通过多维异核核磁共振光谱法，已确定革兰氏阴性土壤细菌黄色粘球菌中钙负载蛋白S（分子量18,792）的溶液结构。蛋白S由四个内部同源基序组成，这些基序排列形成两个具有伪二重对称轴的结构域，整体类似于三棱柱。每个结构域由两个拓扑不等价的“希腊钥匙”组成：第二个和第四个基序形成标准的希腊钥匙，而第一个和第三个基序除了通常的四条β链外，各自还包含一个规则的α螺旋。蛋白S的结构与脊椎动物眼晶状体βγ-晶状体蛋白的结构相似，后者被认为与蛋白S在进化上相关。蛋白S和βγ-晶状体蛋白都通过形成稳定的多分子聚集体发挥作用。然而，蛋白S具有独特的基序组织和结构域堆积，表明其寡聚化模式不同，且与βγ-晶状体蛋白的进化途径不同。
