Najmudin S, Nalini V, Driessen H P, Slingsby C, Blundell T L, Moss D S, Lindley P F
Laboratory of Molecular Biology, Department of Crystallography, Birkbeck College, London, England.
Acta Crystallogr D Biol Crystallogr. 1993 Mar 1;49(Pt 2):223-33. doi: 10.1107/S0907444992007601.
The molecular structure of calf gammaB-crystallin (previously called gammaII), a lens-specific protein, has been refined to a crystallographic R factor of 18.1% for all reflection data, between 8.0 and 1.47 A, 25 959 hkl measured at 293 (1) K. 230 water molecules have been defined by difference Fourier techniques and included in a restrained least-squares refinement. Difference Fourier maps clearly indicated the presence of multiple sites for the sulfur atoms of Cys 18 and Cys 22 which were therefore given coupled second-site occupancies during the refinement. The sulfur atom in the major position of Cys 22 is in the reduced state. Either of the Cys 18 sites can form a high-energy disulfide bridge with the minor position of Cys 22. The position of the carboxy terminus and many other surface side chains have been further defined including the RGD signal peptide. The hydration of the backbone and the interdomain region has been analysed. 27 water molecules make extensive contacts to a single protein molecule and thus contribute to its stability.
小牛γB-晶状体蛋白（以前称为γII）是一种晶状体特异性蛋白，其分子结构已针对所有在8.0至1.47 Å之间、于293（1）K下测量的25959个hkl反射数据，精修至晶体学R因子为18.1%。通过差值傅里叶技术确定了230个水分子，并将其纳入约束最小二乘精修中。差值傅里叶图清楚地表明存在半胱氨酸18和半胱氨酸22硫原子的多个位点，因此在精修过程中为它们赋予了耦合的第二位点占有率。半胱氨酸22主要位置的硫原子处于还原状态。半胱氨酸18的任何一个位点都可以与半胱氨酸22的次要位置形成高能二硫键。羧基末端和许多其他表面侧链的位置已进一步确定，包括RGD信号肽。已分析了主链和结构域间区域的水合作用。27个水分子与单个蛋白质分子有广泛接触，从而有助于其稳定性。
