title: Structural insight into the oxidation of sinapic acid by CotA laccase.
abstract: Laccases can oxidize plenty of substrates by use of molecular oxygen as the final electron acceptor. The broad substrate spectrum is further expanded by using redox mediators in so-called laccase-mediator systems, but the structural studies on interactions between laccases and natural mediators are still absent. In this study, the crystal structure of CotA/sinapic acid complex is solved, structural comparison has revealed a novel substrate binding mode. The residue of His419 instead of His497 is bonding to the sinapic acid (SA) as the primary electron acceptor. Moreover, the binding of SA leads to 10° rotation on Arg416, our mutagenesis data exhibits that the residue Arg416 is crucial in the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and syringaldazine (SGZ). Furthermore, oxidation of several phenolic acids and one non-phenolic acid by CotA was investigated. By analyzing interactions between CotA and SA, it is indicated that the presence of methoxy groups in the ortho-position of the phenolic structure is crucial for the substrate recognition by CotA laccase. This work establishes structure-function relationships for laccase-natural mediator system.
authors: Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China; Key Laboratory of Environmental Microbiology of Sichuan Province, Chengdu 610041, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors: Tian
authors: T
authors: Xie
authors: Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China; Key Laboratory of Environmental Microbiology of Sichuan Province, Chengdu 610041, China.
authors: Zhongchuan
authors: Z
authors: Liu
authors: Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China; Key Laboratory of Environmental Microbiology of Sichuan Province, Chengdu 610041, China.
authors: Qian
authors: Q
authors: Liu
authors: Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China; Key Laboratory of Environmental Microbiology of Sichuan Province, Chengdu 610041, China. Electronic address: wanggg@cib.ac.cn.
authors: Ganggang
authors: G
authors: Wang
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D003373:Coumaric Acids / Q000378:metabolism*; D003460:Crystallization; D042845:Laccase / Q000737:chemistry* / Q000378:metabolism*; D013058:Mass Spectrometry; D008958:Models, Molecular; D010084:Oxidation-Reduction; D016133:Polymerase Chain Reaction; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D003373:Coumaric Acids; C073734:sinapinic acid; C533003:CotA protein, Bacillus licheniformis; D042845:Laccase
keywords: Laccase; Mediator; Mutagenesis; Sinapic acid; Substrate binding