title: Cell-surface Attachment of Bacterial Multienzyme Complexes Involves Highly Dynamic Protein-Protein Anchors.
abstract: Protein-protein interactions play a pivotal role in the assembly of the cellulosome, one of nature's most intricate nanomachines dedicated to the depolymerization of complex carbohydrates. The integration of cellulosomal components usually occurs through the binding of type I dockerin modules located at the C terminus of the enzymes to cohesin modules located in the primary scaffoldin subunit. Cellulosomes are typically recruited to the cell surface via type II cohesin-dockerin interactions established between primary and cell-surface anchoring scaffoldin subunits. In contrast with type II interactions, type I dockerins usually display a dual binding mode that may allow increased conformational flexibility during cellulosome assembly. Acetivibrio cellulolyticus produces a highly complex cellulosome comprising an unusual adaptor scaffoldin, ScaB, which mediates the interaction between the primary scaffoldin, ScaA, through type II cohesin-dockerin interactions and the anchoring scaffoldin, ScaC, via type I cohesin-dockerin interactions. Here, we report the crystal structure of the type I ScaB dockerin in complex with a type I ScaC cohesin in two distinct orientations. The data show that the ScaB dockerin displays structural symmetry, reflected by the presence of two essentially identical binding surfaces. The complex interface is more extensive than those observed in other type I complexes, which results in an ultra-high affinity interaction (Ka ∼10(12) M). A subset of ScaB dockerin residues was also identified as modulating the specificity of type I cohesin-dockerin interactions in A. cellulolyticus. This report reveals that recruitment of cellulosomes onto the cell surface may involve dockerins presenting a dual binding mode to incorporate additional flexibility into the quaternary structure of highly populated multienzyme complexes.
authors: From the CIISA-Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
authors: Kate
authors: K
authors: Cameron
authors: From the CIISA-Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal, shabir@fmv.ulisboa.pt.
authors: Shabir
authors: S
authors: Najmudin
authors: From the CIISA-Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
authors: Victor D
authors: VD
authors: Alves
authors: the Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors: Edward A
authors: EA
authors: Bayer
authors: the Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada, and.
authors: Steven P
authors: SP
authors: Smith
authors: From the CIISA-Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
authors: Pedro
authors: P
authors: Bule
authors: the Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom.
authors: Helen
authors: H
authors: Waller
authors: From the CIISA-Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
authors: Luís M A
authors: LM
authors: Ferreira
authors: the Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Newcastle upon Tyne NE2 4HH, United Kingdom.
authors: Harry J
authors: HJ
authors: Gilbert
authors: From the CIISA-Faculdade de Medicina Veterinária, ULisboa, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal, cafontes@fmv.ulisboa.pt.
authors: Carlos M G A
authors: CM
authors: Fontes
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism; D044603:Cellulosomes / Q000737:chemistry / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D006094:Gram-Positive Bacteria / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D020349:Surface Plasmon Resonance; D000097722:Cohesins
chemical_list: D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D000097722:Cohesins
keywords: cell surface; cell-surface attachment; cellulase; cellulose; cellulosome; protein-protein interaction