Timkovich R, Bergmann D, Arciero D M, Hooper A B
Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487-0336, USA.
Biophys J. 1998 Oct;75(4):1964-72. doi: 10.1016/S0006-3495(98)77637-4.
Cytochrome c-552 from Nitrosomonas europaea is a 9.1-kDa monoheme protein that is a member of the bacterial cytochrome c-551 family. The gene encoding for c-552 has been cloned and sequenced and the primary sequence of the product deduced. Proton resonance assignments were made for all main-chain and most side-chain protons in the diamagnetic, reduced form by two-dimensional NMR techniques. Distance constraints (1056) were determined from nuclear Overhauser enhancements, and torsion angle constraints (88) were determined from scalar coupling estimates. Solution conformations for the protein were computed by the hybrid distance geometry-simulated annealing approach. For 20 computed structures, the root mean squared deviation from the average position of equivalent atoms was 0.84 A (sigma = 0.12) for backbone atoms over all residues. Analysis by residue revealed there were three regions clearly less well defined than the rest of the protein: the first two residues at the N-terminus, the last two at the C-terminus, and a loop region from residues 34 to 40. Omitting these regions from the comparison, the root mean squared deviation was 0.61 A (sigma = 0.13) for backbone atoms, 0.86 A (sigma = 0.12) for all associated heavy atoms, and 0. 43 A (sigma = 0.17) for the heme group. The global folding of the protein is consistent with others in the c-551 family. A deletion at the N-terminus relative to other family members had no impact on the global folding, whereas an insertion at residue 65 did affect the way the polypeptide packs against the methionine-ligated side of the heme. The effects of specific substitutions will be discussed. The structure of c-552 serves to delineate essential features of the c-551 family.
来自欧洲亚硝化单胞菌的细胞色素c-552是一种9.1 kDa的单血红素蛋白，属于细菌细胞色素c-551家族。编码c-552的基因已被克隆和测序，并推导了产物的一级序列。通过二维核磁共振技术对抗磁性还原形式的所有主链和大多数侧链质子进行了质子共振归属。根据核Overhauser增强确定了距离约束（1056个），并根据标量耦合估计确定了扭转角约束（88个）。通过混合距离几何-模拟退火方法计算了该蛋白的溶液构象。对于20个计算结构，所有残基上主链原子相对于等效原子平均位置的均方根偏差为0.84 Å（标准差=0.12）。按残基分析表明，有三个区域的定义明显不如蛋白的其他部分：N端的前两个残基、C端的后两个残基以及34至40位残基的环区。在比较中省略这些区域后，主链原子的均方根偏差为0.61 Å（标准差=0.13），所有相关重原子的均方根偏差为0.86 Å（标准差=0.12），血红素基团的均方根偏差为0.43 Å（标准差=0.17）。该蛋白的整体折叠与c-551家族中的其他蛋白一致。相对于其他家族成员，N端的缺失对整体折叠没有影响，而65位残基处的插入确实影响了多肽与血红素甲硫氨酸连接侧的堆积方式。将讨论特定取代的影响。c-552的结构有助于描绘c-551家族的基本特征。
