Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Suipacha 531, S2002LRK Rosario, Argentina.
Biochemistry. 2010 Sep 14;49(36):7930-8. doi: 10.1021/bi100894r.
Subclass B1 beta-lactamases are Zn(II)-dependent hydrolases that confer bacterial resistance to most clinically useful beta-lactam antibiotics. The enzyme BcII from Bacillus cereus is a prototypical enzyme that belongs to this group, the first Zn(II)-dependent beta-lactamase to be discovered. Crucial aspects of the BcII catalytic mechanism and metal binding mode have been assessed mostly on the Co(II)-substituted surrogate. Here we report a high-resolution structure of Co(II)-BcII, revealing a metal coordination geometry identical to that of the native zinc enzyme. In addition, a high-resolution structure of the apoenzyme, together with structures with different degrees of metal occupancy and oxidation levels of a conserved Cys ligand, discloses a considerable mobility of two loops containing four metal ligands (namely, regions His116-Arg121 and Gly219-Cys221). This flexibility is expected to assist in the structural rearrangement of the metal sites during catalytic turnover, which, along with the coordination geometry adaptability of Zn(II) ions, grants the interaction with a variety of substrates, a characteristic feature of B1 metallo-beta-lactamases.
B1 类β-内酰胺酶是依赖 Zn(II)的水解酶，使细菌对大多数临床有用的β-内酰胺抗生素产生耐药性。蜡状芽孢杆菌来源的 BcII 酶是属于这一组的典型酶，是第一个被发现的依赖 Zn(II)的β-内酰胺酶。BcII 催化机制和金属结合模式的关键方面主要在 Co(II)取代的替代物上进行了评估。在这里，我们报告了 Co(II)-BcII 的高分辨率结构，揭示了与天然锌酶相同的金属配位几何形状。此外，apoenzyme 的高分辨率结构，以及具有不同金属占有率和保守 Cys 配体氧化水平的结构，揭示了包含四个金属配体的两个环（即 His116-Arg121 和 Gly219-Cys221 区域）的相当大的可动性。这种灵活性有望在催化周转过程中协助金属位点的结构重排，这与 Zn(II)离子的配位几何适应性一起，赋予了与各种底物的相互作用，这是 B1 类金属β-内酰胺酶的特征。
