Combined Crystal Structure of a Type I Cohesin: MUTATION AND AFFINITY BINDING STUDIES REVEAL STRUCTURAL DETERMINANTS OF COHESIN-DOCKERIN SPECIFICITIES.
Cohesin-dockerin interactions orchestrate the assembly of one of nature's most elaborate multienzyme complexes, the cellulosome. Cellulosomes are produced exclusively by anaerobic microbes and mediate highly efficient hydrolysis of plant structural polysaccharides, such as cellulose and hemicellulose. In the canonical model of cellulosome assembly, type I dockerin modules of the enzymes bind to reiterated type I cohesin modules of a primary scaffoldin. Each type I dockerin contains two highly conserved cohesin-binding sites, which confer quaternary flexibility to the multienzyme complex. The scaffoldin also bears a type II dockerin that anchors the entire complex to the cell surface by binding type II cohesins of anchoring scaffoldins. In Bacteroides cellulosolvens, however, the organization of the cohesin-dockerin types is reversed, whereby type II cohesin-dockerin pairs integrate the enzymes into the primary scaffoldin, and type I modules mediate cellulosome attachment to an anchoring scaffoldin. Here, we report the crystal structure of a type I cohesin from B. cellulosolvens anchoring scaffoldin ScaB to 1.84-Å resolution. The structure resembles other type I cohesins, and the putative dockerin-binding site, centered at β-strands 3, 5, and 6, is likely to be conserved in other B. cellulosolvens type I cohesins. Combined computational modeling, mutagenesis, and affinity-based binding studies revealed similar hydrogen-bonding networks between putative Ser/Asp recognition residues in the dockerin at positions 11/12 and 45/46, suggesting that a dual-binding mode is not exclusive to the integration of enzymes into primary cellulosomes but can also characterize polycellulosome assembly and cell-surface attachment. This general approach may provide valuable structural information of the cohesin-dockerin interface, in lieu of a definitive crystal structure.
From the CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Kate
K
Cameron
the Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100 Israel, and.
Jonathan Y
JY
Weinstein
the Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100 Israel, and.
Olga
O
Zhivin
From the CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Pedro
P
Bule
the Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100 Israel, and.
Sarel J
SJ
Fleishman
From the CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Victor D
VD
Alves
the Institute of Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4HH, United Kingdom.
Harry J
HJ
Gilbert
From the CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Luís M A
LM
Ferreira
From the CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Carlos M G A
CM
Fontes
the Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, 76100 Israel, and Ed.Bayer@weizmann.ac.il.
Edward A
EA
Bayer
From the CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477 Lisboa, Portugal.
Shabir
S
Najmudin
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001439:Bacteroides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D000097722:Cohesins
D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D000097722:Cohesins
cellulase; cellulose; cellulosome; computational biology; computer modeling; protein-protein interaction