的精制结晶结构DD-peptidase penicillin-target酶1.6一项决议。
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凯利JA, Kuzin美联社
的精制结晶结构DD-peptidase penicillin-target酶1.6一项决议。
J杂志。1995年11月24日,254 (2):223 - 36。
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7490745 (在PubMed]
- 文摘
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D-alanyl-D-alanine肽酶的链霉菌属sp。R61是37500道尔顿的胞外酶作为模型膜结合肽酶参与细菌细胞壁的生物合成。这些酶的抑制beta-lactam抗生素最终导致细菌的细胞死亡。x射线晶体结构的R61 D-alanyl-D-alanine肽酶已经解决了使用多个同形置换、模拟退火和最小二乘优化。空间群和单元细胞参数P2 (1) 2 (1) 2 (1) = 51.1, b = 67.3 a和c = 102.4。结构已经被精炼1.6使用2σ数据分辨率晶体r因子为0.148。模型包含347个残基(2938个原子)和254溶剂分子。整体温度系数是9.6 A2,估计坐标误差是0.14。蛋白质由单一多肽链组织成两个区域。一个区域包含一个nine-stranded反平行的β褶板和螺旋在两面;这个地区包括氨基和羧基末端。 The second region is all helical. Sixty percent of the residues occur in helices or beta-sheet. The reactive Ser62 is found between the two regions of the enzyme at the amino end of the protein's longest-helix which begins with one turn of 3(10) helix and continues with four turns of alpha-helix. The active site is an elongated pocket that contains four basic and four aromatic residues. An oxyanion hole is formed by Ser62 NH and Thr301 NH. The pocket also contains the few key residues that are conserved in all penicillin-binding proteins and beta-lactamases. Two of these residues, Lys65 and Tyr159, are among the 16 side-chains that take on multiple conformations in the R61 crystal structure. Three of the 12 proline rings adopt two conformations which we believe has not been previously reported. There is no anionic acid equivalent to the catalytic Glu166 found in Class A beta-lactamases. Two ordered water molecules (O507 and O644) are found buried in the active site and hydrogen-bonded to each other (2.6 A). O507 could potentially act as the hydrolytic water molecule for deacylation.