Substrate Recognition Mechanism and Substrate-Dependent Conformational Changes of an ROK Family Glucokinase from Streptomyces griseus
Substrate Recognition Mechanism and Substrate-Dependent Conformational Changes of an ROK Family Glucokinase from Streptomyces griseus
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DOI：
10.1128/jb.06173-11
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发表时间：
2011-11
影响因子：
3.2
通讯作者：
K. Miyazono;Nobumitsu Tabei;S. Morita;Y. Ohnishi;S. Horinouchi;M. Tanokura
中科院分区：
文献类型：
--
作者：
K. Miyazono;Nobumitsu Tabei;S. Morita;Y. Ohnishi;S. Horinouchi;M. Tanokura
摘要碳分解代谢抑制(CCR)是许多细菌中普遍存在的一种现象，它被定义为在较佳碳源存在的情况下，对不利碳源的分解代谢酶活性的抑制。在链霉菌中，次生代谢产物的产生往往受到碳源的负面影响，这表明Ccr参与了次生代谢。虽然链霉菌的CCR机制尚不清楚，但葡糖激酶可能是CCR的核心角色。SgGlkA是一种来自灰链霉菌的葡萄糖激酶，属于韩国葡萄糖激酶家族，有两个共同的序列基序(1和2)。在这里，我们报道了apo-SgGlkA，SgGlkA与葡萄糖的络合物，以及SgGlkA与葡萄糖和腺苷酰亚胺二磷酸(AMPPNP)的络合物的晶体结构，这是韩国葡萄糖激酶家族的第一个结构。SgGlkA分为一个小的α/β结构域和一个大的α+β结构域，它形成二聚体四聚体构型。SgGlkA在这两个结构域之间结合了一个葡萄糖的β异构体，而共识序列1中的His157在SgGlkA的葡萄糖结合机制和异构体专一性中起着重要作用。在SgGlkA的结构中，His157与一致序列2中的三个半胱氨酸残基形成一个HC3型锌指基序，与锌离子结合，并与葡萄糖的C1和C2羟基形成两个氢键。当比较这三种结构时，发现SgGlkA的结构通过底物的结合而改变。链霉菌中SgGlkA依赖底物的构象变化可能与CCR机制有关。
ABSTRACT Carbon catabolite repression (CCR) is a widespread phenomenon in many bacteria that is defined as the repression of catabolic enzyme activities for an unfavorable carbon source by the presence of a preferable carbon source. In Streptomyces, secondary metabolite production often is negatively affected by the carbon source, indicating the involvement of CCR in secondary metabolism. Although the CCR mechanism in Streptomyces still is unclear, glucokinase is presumably a central player in CCR. SgGlkA, a glucokinase from S. griseus, belongs to the ROK family glucokinases, which have two consensus sequence motifs (1 and 2). Here, we report the crystal structures of apo-SgGlkA, SgGlkA in complex with glucose, and SgGlkA in complex with glucose and adenylyl imidodiphosphate (AMPPNP), which are the first structures of an ROK family glucokinase. SgGlkA is divided into a small α/β domain and a large α+β domain, and it forms a dimer-of-dimer tetrameric configuration. SgGlkA binds a β-anomer of glucose between the two domains, and His157 in consensus sequence 1 plays an important role in the glucose-binding mechanism and anomer specificity of SgGlkA. In the structures of SgGlkA, His157 forms an HC3-type zinc finger motif with three cysteine residues in consensus sequence 2 to bind a zinc ion, and it forms two hydrogen bonds with the C1 and C2 hydroxyls of glucose. When the three structures are compared, the structure of SgGlkA is found to be modified by the binding of substrates. The substrate-dependent conformational changes of SgGlkA may be related to the CCR mechanism in Streptomyces.