title: Integration of bacterial expansin-like proteins into cellulosome promotes the cellulose degradation.
abstract: Cellulosomes are multi-enzyme complexes assembled by cellulases and hemicellulases through dockerin-cohesin interactions, which are the most efficient system for the degradation of lignocellulosic resources in nature. Recent genomic analysis of a cellulosome-producing anaerobe Clostridium clariflavum DSM 19732 revealed that two expansin-like proteins, Clocl_1298 and Clocl_1862, contain a dockerin module, which suggests that they are components of the cellulosome. Bacterial expansin-like proteins do not have hydrolytic activities, but can facilitate the degradation of cellulosic biomass via synergistic effects with cellulases. In this study, the synergistic effect of the expansin-like proteins with both native and designer cellulosomes was investigated. The free expansin-like proteins, including expansin-like domains of Clocl_1298 and Clocl_1862, as well as a well-studied bacterial expansin-like protein BsEXLX1 from Bacillus subtilis, promoted the cellulose degradation by native cellulosomes, indicating the cellulosomal expansin-like proteins have the synergistic function. When they were integrated into a trivalent designer cellulosome, the synergistic effect was further amplified. The sequence and structure analyses indicated that these cellulosomal expansin-like proteins share the conserved functional mechanism with other bacterial expansin-like proteins. These results indicated that non-catalytic expansin-like proteins in the cellulosome can enhance the activity of the cellulosome in lignocellulose degradation. The involvement of functional expansin-like proteins in the cellulosome also implies new physiological functions of bacterial expansin-like proteins and cellulosomes.
authors.affiliation: Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Chen
authors.affiliation: Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Zhenling
authors.initials: Z
authors.lastname: Cui
authors.affiliation: Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.
authors.forename: Xiangfei
authors.initials: X
authors.lastname: Song
authors.affiliation: Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.|CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China. cuiqiu@qibebt.ac.cn.|Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China. cuiqiu@qibebt.ac.cn.|CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China. cuiqiu@qibebt.ac.cn.
authors.forename: Qiu
authors.initials: Q
authors.lastname: Cui
authors.affiliation: Qingdao Engineering Laboratory of Single Cell Oil, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China. fengyg@qibebt.ac.cn.|Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China. fengyg@qibebt.ac.cn.|CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao, Shandong, 266101, China. fengyg@qibebt.ac.cn.
authors.forename: Yingang
authors.identifier: http://orcid.org/0000-0002-0879-1316
authors.initials: Y
authors.lastname: Feng
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism*; D001711:Biotransformation; D002482:Cellulose / Q000378:metabolism*; D044603:Cellulosomes / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology* / Q000235:genetics; D006868:Hydrolysis
chemical_list: D001426:Bacterial Proteins; D002482:Cellulose
keywords: Cellulose hydrolysis; Cellulosome; Clostridium clariflavum; Dockerin; Expansin