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Lookup NU author(s): Tibor Nagy, Dr Mark Proctor, Emeritus Professor Harry Gilbert
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The assembly of proteins that display complementary activities into macromolecular complexes is critical to cellular function. One such enzyme complex, of environmental significance, is the plant cell wall degrading apparatus of anaerobic bacteria, termed the cellulosome. The complex assembles through the interaction of enzyme-derived "type I dockerin" modules with the multiple "cohesin" modules of the scaffolding protein. Clostridium thermocellum type I dockerin modules contain a duplicated 22-residue sequence that comprises helix-1 and helix-3, respectively. The crystal structure of a C thermocellum type I cohesin-dockerin complex showed that cohesin recognition was predominantly through helix-3 of the dockerin. The sequence duplication is reflected in near-perfect 2-fold structural symmetry, suggesting that both repeats could interact with cohesins by a common mechanism in wild-type (WT) proteins. Here, a helix-3 disrupted mutant dockerin is used to visualize the reverse binding in which the dockerin mutant is indeed rotated 180° relative to the WT dockerin such that helix-1 now dominates recognition of its protein partner. The dual binding mode is predicted to impart significant plasticity into the orientation of the catalytic subunits within this supramolecular assembly, which reflects the challenges presented by the degradation of a heterogeneous, recalcitrant, insoluble substrate by a tethered macromolecular complex. © 2007 by The National Academy of Sciences of the USA.
Author(s): Carvalho AL, Dias FMV, Nagy T, Prates JAM, Proctor MR, Smith N, Bayer EA, Davies GJ, Ferreira LMA, Romao MJ, Fontes CMGA, Gilbert HJ
Publication type: Article
Publication status: Published
Journal: Proceedings of the National Academy of Sciences of the United States of America
Year: 2007
Volume: 104
Issue: 9
Pages: 3089-3094
ISSN (print): 0027-8424
ISSN (electronic): 1091-6490
Publisher: National Academy of Sciences
URL: http://dx.doi.org/10.1073/pnas.0611173104
DOI: 10.1073/pnas.0611173104
PubMed id: 17360613
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