环状芽孢杆菌环糊精葡萄糖基转移酶的麦芽糖糊精依赖性结晶
Maltodextrin-dependent crystallization of cyclomaltodextrin glucanotransferase from Bacillus circulans.
作者信息
Lawson C L, Bergsma J, Bruinenberg P M, de Vries G, Dijkhuizen L, Dijkstra B W
机构信息
Laboratory of Chemical Physics, University of Groningen, The Netherlands.
出版信息
J Mol Biol. 1990 Aug 20;214(4):807-9. doi: 10.1016/0022-2836(90)90335-J.
Crystals of cyclomaltodextrin glucanotransferase from Bacillus circulans (EC 2.4.1.19) suitable for high-resolution X-ray analysis were obtained by vapor diffusion against 60% (v/v) 2-methyl 2,4-pentanediol buffered with 100 mM-sodium Hepes, pH 7.55. The crystals have P2(1)2(1)2(1) space group symmetry, with a = 120.4 A, b = 110.9 A and c = 66.4 A, and contain one molecule of 68,000 in the asymmetric unit. Growth of single enzyme crystals was found to require the presence of either alpha-cyclodextrin, beta-cyclodextrin, gamma-cyclodextrin, or maltose in high molar excess, a requirement that could not be fulfilled by glucose, the basic building block of these compounds. Although the exact role of cyclic and linear maltodextrins in enzyme crystallization is not yet known, we have preliminary evidence that these compounds are degraded by the enzyme in the crystallization droplet.
通过气相扩散法，以100 mM 4-(2-羟乙基)-1-哌嗪乙磺酸（Hepes）缓冲的60%（v/v）2-甲基-2,4-戊二醇为沉淀剂，获得了适合高分辨率X射线分析的环状芽孢杆菌环麦芽糊精葡糖基转移酶（EC 2.4.1.19）晶体。这些晶体具有P2(1)2(1)2(1)空间群对称性，a = 120.4 Å，b = 110.9 Å，c = 66.4 Å，不对称单元中含有一个68,000 Da的分子。发现单酶晶体的生长需要高摩尔过量的α-环糊精、β-环糊精、γ-环糊精或麦芽糖的存在，而这些化合物的基本组成单元葡萄糖则无法满足这一要求。虽然环状和线性麦芽糊精在酶结晶中的具体作用尚不清楚，但我们有初步证据表明这些化合物在结晶液滴中会被酶降解。
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