Bycroft M, Ludvigsen S, Fersht A R, Poulsen F M
Cambridge Centre for Protein Engineering, University Chemical Laboratory, U.K.
Biochemistry. 1991 Sep 3;30(35):8697-701. doi: 10.1021/bi00099a030.
The solution conformation of the ribonuclease barnase has been determined by using 1H nuclear magnetic resonance (NMR) spectroscopy. The 20 structures were calculated by using 853 interproton distance restraints obtained from analyses of two-dimensional nuclear Overhauser spectra, 72 phi and 53 chi 1 torsion angle restraints, and 17 hydrogen-bond distance restraints. The calculated structures contain two alpha-helices (residues 6-18 and 26-34) and a five-stranded antiparallel beta-sheet (residues 50-55, 70-75, 85-91, 94-101, and 105-108). The core of the protein is formed by the packing of one of the alpha-helices (residues 6-18) onto the beta-sheet. The average RMS deviation between the calculated structures and the mean structure is 1.11 A for the backbone atoms and 1.75 A for all atoms. The protein is least well-defined in the N-terminal region and in three large loops. When these regions are excluded, the average RMS deviation between the calculated structures and the mean structure for residues 5-34, 50-56, 71-76, 85-109 is 0.62 A for the backbone atoms and 1.0 A for all atoms. The NMR-derived structure has been compared with the crystal structure of barnase [Mauguen et al. (1982) Nature (London) 297, 162-164].
已通过使用1H核磁共振（NMR）光谱法确定了核糖核酸酶巴那斯的溶液构象。通过对二维核Overhauser光谱分析获得的853个质子间距离约束、72个φ角和53个χ1扭转角约束以及17个氢键距离约束，计算出了20种结构。计算出的结构包含两个α螺旋（残基6 - 18和26 - 34）和一个五链反平行β折叠（残基50 - 55、70 - 75、85 - 91、94 - 101和105 - 108）。蛋白质的核心是由其中一个α螺旋（残基6 - 18）堆积在β折叠上形成的。计算出的结构与平均结构之间，主链原子的平均均方根偏差为1.11 Å，所有原子的平均均方根偏差为1.75 Å。该蛋白质在N端区域和三个大环中定义最不明确。当排除这些区域时，对于残基5 - 34、50 - 56、71 - 76、85 - 109，计算出的结构与平均结构之间，主链原子的平均均方根偏差为0.62 Å，所有原子的平均均方根偏差为1.0 Å。已将NMR推导的结构与巴那斯的晶体结构进行了比较[Mauguen等人（1982年），《自然》（伦敦）297，162 - 164]。
