Tahirov T H, Oki H, Tsukihara T, Ogasahara K, Yutani K, Libeu C P, Izu Y, Tsunasawa S, Kato I
Institute for Protein Research, Osaka University, Japan.
J Struct Biol. 1998 Jan;121(1):68-72. doi: 10.1006/jsbi.1997.3940.
The monoclinic crystal form of methionine amino-peptidase from Pyrococcus furiosus (MAP-Pfu) has been crystallized from four different conditions. Native crystals belong to space group P2(1) with typical unit-cell dimensions a = 53.4, b = 85.1, c = 72.7 A, beta = 107.7 degrees and diffract to 2.9-4.5 A resolution. However, there is a problem of nonisomorphism among the crystals. Water-mediated transformation to low-humidity form occurs by reduction of the relative humidity of crystal environment to 79%. The unit-cell dimensions of transformed crystals are a = 51.9, b = 83.3, c = 70.3 A, beta = 105.9 degrees, and the calculated solvent content is 3.9% less than in original crystals. Transformation to low-humidity form is accompanied by 1.7 times reduction of overall temperature factors, extension of diffraction resolution up to 1.75 A, without change or reduction of crystal mosaicity, and improvement in stability to X-ray radiation. The water-mediated transformation also appears to relieve the problem of nonisomorphism among the original MAP-Pfu crystals.
来自嗜热栖热菌的甲硫氨酸氨肽酶（MAP-Pfu）的单斜晶型已在四种不同条件下结晶。天然晶体属于空间群P2(1)，典型晶胞参数为a = 53.4、b = 85.1、c = 72.7 Å，β = 107.7°，衍射分辨率为2.9 - 4.5 Å。然而，晶体之间存在非同构问题。通过将晶体环境的相对湿度降低到79%，会发生水介导的向低湿度形式的转变。转变后晶体的晶胞参数为a = 51.9、b = 83.3、c = 70.3 Å，β = 105.9°，计算得到的溶剂含量比原始晶体少3.9%。向低湿度形式的转变伴随着整体温度因子降低1.7倍，衍射分辨率提高到1.75 Å，晶体镶嵌性无变化或降低，并且对X射线辐射的稳定性提高。水介导的转变似乎也缓解了原始MAP-Pfu晶体之间的非同构问题。
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