title: Expression, purification, crystallization and preliminary X-ray analysis of CttA, a putative cellulose-binding protein from Ruminococcus flavefaciens.
abstract: A number of anaerobic microorganisms produce multi-modular, multi-enzyme complexes termed cellulosomes. These extracellular macromolecular nanomachines are designed for the efficient degradation of plant cell-wall carbohydrates to smaller sugars that are subsequently used as a source of carbon and energy. Cellulolytic strains from the rumens of mammals, such as Ruminococcus flavefaciens, have been shown to have one of the most complex cellulosomal systems known. Cellulosome assembly requires the binding of dockerin modules located in cellulosomal enzymes to cohesin modules located in a macromolecular scaffolding protein. Over 220 genes encoding dockerin-containing proteins have been identified in the R. flavefaciens genome. The dockerin-containing enzymes can be incorporated into the primary scaffoldin (ScaA), which in turn can bind to adaptor scaffoldins (ScaB or ScaC) and subsequently to anchoring scaffoldin (ScaE), thereby attaching the whole complex to the cell surface. However, unlike other cellulosomes such as that from Clostridium thermocellum, the Ruminococcus species lack a specific carbohydrate-binding module (CBM) on ScaA which recruits the entire complex onto the surface of the substrate. Instead, a cellulose-binding protein, CttA, comprising two putative tandem novel carbohydrate-binding modules and a C-terminal X-dockerin module, which can bind to the cohesin of ScaE, may mediate the attachment of bacterial cells to cellulose. Here, the expression, purification and crystallization of the carbohydrate-binding modular part of the CttA from R. flavefaciens are described. X-ray data have been collected to resolutions of 3.23 and to 1.61 Å in space groups P3(1)21 or P3(2)21 and P2(1), respectively. The structure was phased using bound iodide from the crystallization buffer by SAD experiments.
authors.affiliation: CIISA, Faculdade de Medicina Veterinaria, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Immacolata
authors.initials: I
authors.lastname: Venditto
authors.affiliation: CIISA, Faculdade de Medicina Veterinaria, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Bule
authors.affiliation: Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, 91192 Gif-sur-Yvette, France.
authors.forename: Andrew
authors.initials: A
authors.lastname: Thompson
authors.affiliation: Diamond Light Source, Harwell Science and Innovation Campus, Chilton, Didcot OX11 0DE, England.
authors.forename: Juan
authors.initials: J
authors.lastname: Sanchez-Weatherby
authors.affiliation: Diamond Light Source, Harwell Science and Innovation Campus, Chilton, Didcot OX11 0DE, England.
authors.forename: James
authors.initials: J
authors.lastname: Sandy
authors.affiliation: CIISA, Faculdade de Medicina Veterinaria, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Luis M A
authors.initials: LM
authors.lastname: Ferreira
authors.affiliation: CIISA, Faculdade de Medicina Veterinaria, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Carlos M G A
authors.initials: CM
authors.lastname: Fontes
authors.affiliation: CIISA, Faculdade de Medicina Veterinaria, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Shabir
authors.initials: S
authors.lastname: Najmudin
mesh_terms: D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics; D002482:Cellulose / Q000737:chemistry*; D044603:Cellulosomes / Q000737:chemistry; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D003460:Crystallization; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D008969:Molecular Sequence Data; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D045857:Ruminococcus / Q000737:chemistry* / Q000378:metabolism; D000097722:Cohesins
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002482:Cellulose; D002868:Chromosomal Proteins, Non-Histone; D020033:Protein Isoforms; D011994:Recombinant Proteins; D000097722:Cohesins
keywords: CttA; Ruminococcus flavefaciens; X-dockerin; cell surface attachment; cellulose-binding protein; cellulosome