A Distal Disulfide Bridge in OXA-1 beta-Lactamase Stabilizes the Catalytic Center and Alters the Dynamics of the Specificity Determining Omega Loop

作者：Simakov Nikolay; Leonard David A; Smith Jeremy C; Wymore Troy; Szarecka Agnieszka^*

来源：Journal of Physical Chemistry B, 2017, 121(15): 3285-3296.

DOI：10.1021/acs.jpcb.6b07884

Widespread antibiotic resistance, particularly when mediated by broad-spectrum beta-lactamases, has major implications for public health. Substitutions in the active site often allow broad-spectrum enzymes to accommodate diverse types of beta-lactams. Substitutions observed outside the active site are thought to compensate for the loss of thermal stability. The OXA-1 clade of class D beta-lactamases contains a pair of conserved cysteines locate outside the active site that forms a disulfide bond in the periplasm. Here, the effect of the distal disulfide bond on the structure and dynamics of OXA-1 was investigated via 4 mu s molecular dynamics simulations. The results reveal that the disulfide promotes the preorganized orientation of the catalytic residues and affects the conformation of the functionally important Omega loop. FurtherMore, principal component analysis reveals differences in the global dynamics between the oxidized and reduced forms, especially in the motions involving the Omega. loop. A dynamical network analysis indicates that, in the oxidized form, in addition to its role in ligand binding, the KTG family motif is a central hub of the global dynamics. As activity of OXA-1 has been measured only in the reduced form, we suggest that accurate assessment of its functional profile would require oxidative conditions mimicking periplasm.

• 出版日期2017-4-20