title: Small angle X-ray scattering analysis of Clostridium thermocellum cellulosome N-terminal complexes reveals a highly dynamic structure.
abstract: Clostridium thermocellum produces the prototypical cellulosome, a large multienzyme complex that efficiently hydrolyzes plant cell wall polysaccharides into fermentable sugars. This ability has garnered great interest in its potential application in biofuel production. The core non-catalytic scaffoldin subunit, CipA, bears nine type I cohesin modules that interact with the type I dockerin modules of secreted hydrolytic enzymes and promotes catalytic synergy. Because the large size and flexibility of the cellulosome preclude structural determination by traditional means, the structural basis of this synergy remains unclear. Small angle x-ray scattering has been successfully applied to the study of flexible proteins. Here, we used small angle x-ray scattering to determine the solution structure and to analyze the conformational flexibility of two overlapping N-terminal cellulosomal scaffoldin fragments comprising two type I cohesin modules and the cellulose-specific carbohydrate-binding module from CipA in complex with Cel8A cellulases. The pair distribution functions, ab initio envelopes, and rigid body models generated for these two complexes reveal extended structures. These two N-terminal cellulosomal fragments are highly dynamic and display no preference for extended or compact conformations. Overall, our work reveals structural and dynamic features of the N terminus of the CipA scaffoldin that may aid in cellulosome substrate recognition and binding.
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada.
authors: Mark A
authors: MA
authors: Currie
authors: Centro Interdisciplinar de Investigacao em Sanidade Animal, Faculdade de Medincina Veterinaria, Universidade Tecnica de Lisboa, 1300-477 Lisbon, Portugal.
authors: Kate
authors: K
authors: Cameron
authors: Centro Interdisciplinar de Investigacao em Sanidade Animal, Faculdade de Medincina Veterinaria, Universidade Tecnica de Lisboa, 1300-477 Lisbon, Portugal.
authors: Fernando M V
authors: FMV
authors: Dias
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada.
authors: Holly L
authors: HL
authors: Spencer
authors: Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors: Edward A
authors: EA
authors: Bayer
authors: Centro Interdisciplinar de Investigacao em Sanidade Animal, Faculdade de Medincina Veterinaria, Universidade Tecnica de Lisboa, 1300-477 Lisbon, Portugal.
authors: Carlos M G A
authors: CMGA
authors: Fontes
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada; Protein Function Discovery Group, Queen's University, Kingston, Ontario K7L 3N6, Canada. Electronic address: steven.smith@queensu.ca.
authors: Steven P
authors: SP
authors: Smith
authors: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada; Protein Function Discovery Group, Queen's University, Kingston, Ontario K7L 3N6, Canada. Electronic address: jia@queensu.ca.
authors: Zongchao
authors: Z
authors: Jia
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002352:Carrier Proteins / Q000737:chemistry*; D002480:Cellulase / Q000737:chemistry* / Q000378:metabolism; D048013:Acetivibrio thermocellus / Q000378:metabolism*; D018360:Crystallography, X-Ray / Q000379:methods; D008958:Models, Molecular; D008968:Molecular Conformation; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D053838:Scattering, Small Angle; D013379:Substrate Specificity; D014965:X-Rays
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; C473132:cellulosome, Clostridium; C074074:cellulose binding protein A, Clostridium cellulovorans; D002480:Cellulase