CRYSTAL-STRUCTURE OF PROTEUS-MIRABILIS PR CATALASE WITH AND WITHOUT BOUND NADPH
CRYSTAL-STRUCTURE OF PROTEUS-MIRABILIS PR CATALASE WITH AND WITHOUT BOUND NADPH
复制标题
DOI：
10.1006/jmbi.1995.0350
复制
发表时间：
1995-06-23
影响因子：
5.6
通讯作者：
DIDEBERG, O
中科院分区：
文献类型：
--
作者：
GOUET, P;JOUVE, HM;DIDEBERG, O
来自奇异变形杆菌过氧化物抗性突变体的过氧化氢酶与 NADPH 紧密结合。有趣的是，这种酶可以去除 NADPH 而不会损失过氧化氢活性。它是唯一已知的能够结合 NADPH 的非哺乳动物过氧化氢酶。以牛肝过氧化氢酶结构为模型，通过分子置换解决了不含辅因子的结构。该结构在 8 至 2.2 埃分辨率范围内被细化至 19.3% 的 R 因子。根据序列，甲硫氨酸砜位于血红素活性位点。这种氧化形式的蛋氨酸是奇异变形杆菌过氧化氢酶所特有的，并且可能在活性位点产生一些空间位阻。两个重要的水分子位于血红素远端部位。这两个水分子并不位于牛肝过氧化氢酶的结构中，但应该解释其催化机制。通过将未配体形式的晶体浸泡到NADPH溶液中获得配体形式。使用未配体结构作为模型，在 8 至 3.1 埃分辨率范围内将结构细化至 15.9% 的 X 因子。 NADPH在电子密度图中清晰可见，其构象与牛肝过氧化氢酶相同。 NADPH 结合会引起轻微的结构变化。然而，组氨酸残基 (His284) 的咪唑环旋转约 50 度以容纳辅因子。检查了从 NADPH 到血红素分子的电子转移，并提出了几种途径。
A catalase from a peroxide resistant mutant of Proteus mirabilis binds NADPH tightly. Interestingly, this enzyme can be stripped of NADPH without loss of the catalatic activity It is the only known non-mammalian catalase able to bind NADPH. The structure without cofactor was solved by molecular replacement using the structure of beef liver catalase as a model. The structure was refined to an R-factor of 19.3% in the range 8 to 2.2 Angstrom resolution. According to the sequence, a methionine sulphone was positioned in the haem active site. This oxidized form of methionine is particular to Proteus mirabilis catalase and likely to produce some steric hindrance in the active site. Two important water molecules are positioned in the haem distal site. These two water molecules are not located in the structure of beef liver catalase, but are supposed to account for the catalytic mechanism. The liganded form was obtained by soaking crystals of the unliganded form into an NADPH solution. The structure was refined to an X-factor of 15.9% in the range of 8 to 3.1 Angstrom resolution using the unliganded structure as a model. The NADPH was clearly located in the electron density map with the same conformation as in beef liver catalase. The NADPH binding induces slight structural changes. However, the imidazole ring of a histidine residue (His284) rotates about 50 degrees to accommodate the cofactor. The electron transfer from NADPH to the haem molecule was examined and several pathways are proposed.