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Noncellulosomal cohesin- and dockerin-like modules in the three domains of life.

ABSTRACT: The high-affinity cohesin-dockerin interaction was originally discovered as modular components, which mediate the assembly of the various subunits of the multienzyme cellulosome complex that characterizes some cellulolytic bacteria. Until recently, the presence of cohesins and dockerins within a bacterial proteome was considered a definitive signature of a cellulosome-producing bacterium. Widespread genome sequencing has since revealed a wealth of putative cohesin- and dockerin-containing proteins in Bacteria, Archaea, and in primitive eukaryotes. The newly identified modules appear to serve diverse functions that are clearly distinct from the classical cellulosome archetype, and the vast majority of parent proteins are not predicted glycoside hydrolases. In most cases, only a few such genes have been identified in a given microorganism, which encode proteins containing but a single cohesin and/or dockerin. In some cases, one or the other module appears to be missing from a given species, and in other cases both modules occur within the same protein. This review provides a bioinformatics-based survey of the current status of cohesin- and dockerin-like sequences in species from the Bacteria, Archaea, and Eukarya. Surprisingly, many identified modules and their parent proteins are clearly unrelated to cellulosomes. The cellulosome paradigm may thus be the exception rather than the rule for bacterial, archaeal, and eukaryotic employment of cohesin and dockerin modules.

SUBMITTER: Peer A

PROVIDER: S-EPMC3035643 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Noncellulosomal cohesin- and dockerin-like modules in the three domains of life.

Peer Ayelet A Smith Steven P SP Bayer Edward A EA Lamed Raphael R Borovok Ilya I

FEMS microbiology letters 20081118 1

The high-affinity cohesin-dockerin interaction was originally discovered as modular components, which mediate the assembly of the various subunits of the multienzyme cellulosome complex that characterizes some cellulolytic bacteria. Until recently, the presence of cohesins and dockerins within a bacterial proteome was considered a definitive signature of a cellulosome-producing bacterium. Widespread genome sequencing has since revealed a wealth of putative cohesin- and dockerin-containing protei ...[more]

PMID: 19025568

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Project description:Cellulosic waste represents a significant and underutilized carbon source for the biofuel industry. Owing to the recalcitrance of crystalline cellulose to enzymatic degradation, it is necessary to design economical methods of liberating the fermentable sugars required for bioethanol production. One route towards unlocking the potential of cellulosic waste lies in a highly complex class of molecular machines, the cellulosomes. Secreted mainly by anaerobic bacteria, cellulosomes are structurally diverse, cell surface-bound protein assemblies that can contain dozens of catalytic components. The key feature of the cellulosome is its modularity, facilitated by the ultra-high affinity cohesin-dockerin interaction. Due to the enormous number of cohesin and dockerin modules found in a typical cellulolytic organism, a major bottleneck in understanding the biology of cellulosomics is the purification of each cohesin- and dockerin-containing component, prior to analyses of their interaction. As opposed to previous approaches, the present study utilized proteins contained in unpurified whole-cell extracts. This strategy was made possible due to an experimental design that allowed for the relevant proteins to be "purified" via targeted affinity interactions as a function of the binding assay. The approach thus represents a new strategy, appropriate for future medium- to high-throughput screening of whole genomes, to determine the interactions between cohesins and dockerins. We have selected the cellulosome of Acetivibrio cellulolyticus for this work due to its exceptionally complex cellulosome systems and intriguing diversity of its cellulosomal modular components. Containing 41 cohesins and 143 dockerins, A. cellulolyticus has one of the largest number of potential cohesin-dockerin interactions of any organism, and contains unusual and novel cellulosomal features. We have surveyed a representative library of cohesin and dockerin modules spanning the cellulosome's total cohesin and dockerin sequence diversity, emphasizing the testing of unusual and previously-unknown protein modules. The screen revealed several novel cell-bound cellulosome architectures, thus expanding on those previously known, as well as soluble cellulose systems that are not bound to the bacterial cell surface. This study sets the stage for screening the entire complement of cellulosomal components from A. cellulolyticus and other organisms with large cellulosome systems. The knowledge gained by such efforts brings us closer to understanding the exceptional catalytic abilities of cellulosomes and will allow the use of novel cellulosomal components in artificial assemblies and in enzyme cocktails for sustainable energy-related research programs.

Dataset Information

Noncellulosomal cohesin- and dockerin-like modules in the three domains of life.

Publications

Noncellulosomal cohesin- and dockerin-like modules in the three domains of life.

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