title: Characterization of a cellulosome dockerin domain from the anaerobic fungus Piromyces equi.
abstract: The recycling of photosynthetically fixed carbon in plant cell walls is a key microbial process. In anaerobes, the degradation is carried out by a high molecular weight multifunctional complex termed the cellulosome. This consists of a number of independent enzyme components, each of which contains a conserved dockerin domain, which functions to bind the enzyme to a cohesin domain within the protein scaffoldin protein. Here we describe the first three-dimensional structure of a fungal dockerin, the N-terminal dockerin of Cel45A from the anaerobic fungus Piromyces equi. The structure contains a novel fold of 42 residues. The ligand binding site consists of residues Trp 35, Tyr 8 and Asp 23, which are conserved in all fungal dockerins. The binding site is on the opposite side of the N- and C-termini of the molecule, implying that tandem dockerin domains, seen in the majority of anaerobic fungal plant cell wall degrading enzymes, could present multiple simultaneous binding sites and, therefore, permit tailoring of binding to catalytic demands.
authors.affiliation: Department of Molecular Biology and Biotechnology, Krebs Institute, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: S
authors.initials: S
authors.lastname: Raghothama
authors.forename: R Y
authors.initials: RY
authors.lastname: Eberhardt
authors.forename: P
authors.initials: P
authors.lastname: Simpson
authors.forename: D
authors.initials: D
authors.lastname: Wigelsworth
authors.forename: P
authors.initials: P
authors.lastname: White
authors.forename: G P
authors.initials: GP
authors.lastname: Hazlewood
authors.forename: T
authors.initials: T
authors.lastname: Nagy
authors.forename: H J
authors.initials: HJ
authors.lastname: Gilbert
authors.forename: M P
authors.initials: MP
authors.lastname: Williamson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D017124:Conserved Sequence; D020832:EF Hand Motifs; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005658:Fungi / Q000737:chemistry* / Q000235:genetics; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013816:Thermodynamics; D000097722:Cohesins
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D005656:Fungal Proteins; D008024:Ligands; D009687:Nuclear Proteins; D000097722:Cohesins; C435103:CEL45A protein, Piromyces equi