Rypniewski W R, Holden H M, Rayment I
EMBL c/o DESY, Hamburg, Germany.
Biochemistry. 1993 Sep 21;32(37):9851-8. doi: 10.1021/bi00088a041.
Chemical modification of proteins has been and continues to be an important biochemical tool for the study of protein structure and function. One such type of approach has been the reductive methylation of lysine residues. In order to address the consequences of such methylation on the crystallization and structural properties of a protein, the three-dimensional structure of hen egg white lysozyme in which all lysine residues have been alkylated has been determined and refined to a nominal resolution of 1.8 A and a crystallographic R factor of 17.3%. Crystals used in the investigation were grown from 1.5-1.8 M MgSO4 and 50 mM Tris at pH 8.0 and belonged to the space group P2(1)2(1)2(1) with unit cell dimensions of a = 30.6 A, b = 56.3 A, c = 73.2 A, and one molecule per asymmetric unit. It was not possible to grow crystals of the modified lysozyme under the conditions normally employed for the hen egg white protein. Overall, the three-dimensional structures of the native lysozyme and the modified protein are very similar with only two surface loops differing to any significant extent. Specifically, the positions of the alpha-carbons for these two forms of the protein, excluding the surface loops, superimpose with a root-mean-square value of 0.40 A. The magnitude of the structural changes observed between the modified an unmodified forms of lysozyme is similar to that seen when an identical protein structure is solved in two different crystalline lattices.(ABSTRACT TRUNCATED AT 250 WORDS)
蛋白质的化学修饰一直是且仍然是研究蛋白质结构和功能的重要生化工具。其中一种方法是赖氨酸残基的还原甲基化。为了研究这种甲基化对蛋白质结晶和结构性质的影响，已确定并精修了所有赖氨酸残基均已烷基化的鸡蛋清溶菌酶的三维结构，标称分辨率为1.8 Å，晶体学R因子为17.3%。研究中使用的晶体是在1.5 - 1.8 M MgSO4和pH 8.0的50 mM Tris中生长的，属于空间群P2(1)2(1)2(1)，晶胞尺寸为a = 30.6 Å，b = 56.3 Å，c = 73.2 Å，每个不对称单元有一个分子。在通常用于鸡蛋清蛋白的条件下无法生长修饰溶菌酶的晶体。总体而言，天然溶菌酶和修饰蛋白的三维结构非常相似，只有两个表面环有显著差异。具体来说，这两种形式的蛋白质（不包括表面环）的α-碳原子位置叠加时的均方根值为0.40 Å。修饰型和未修饰型溶菌酶之间观察到的结构变化幅度与在两种不同晶格中解析相同蛋白质结构时看到的相似。（摘要截短至250字）
