Intermodular Linker Flexibility Revealed from Crystal Structures of Adjacent Cellulosomal Cohesins of Acetivibrio cellulolyticus

Ilit Noach, Felix Frolow*, Orly Alber, Raphael Lamed, Linda J.W. Shimon, Edward A. Bayer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Cellulosome complexes comprise an intercalated set of multimodular dockerin-containing enzymatic subunits connected to cohesin-containing nonenzymatic subunits called scaffoldins. The adjoining modules in each cellulosomal subunit are interconnected by a variety of linker segments of different lengths and composition. The exact role of the cellulosomal linkers has yet to be described, although it is assumed that they contribute to the architecture and action of the cellulosome by providing the protein subunits with flexibility and by providing spacers between the enzymatic modules that could enhance interactions with the cellulose substrate. Here we present four crystal structures of Acetivibrio cellulolyticus cellulosomal type II cohesins with linker extensions. Two of the structures represent two different crystal forms (trigonal and orthorhombic) of the same N-terminal cohesin module (CohB1) together with its full (6-residue) native C-terminal linker, derived from scaffoldin B. The other two structures belong to the adjacent (second) cohesin module (CohB2), each of which was crystallized with the same 6-residue linker segment, but now positioned at the N-terminus and with either a truncated (5-residue) or a full-length (45-residue) C-terminal linker, respectively. Comparison between the two CohB1 structures revealed significant differences in the conformation of their equivalent C-terminal linker segment. In one crystal form a helical conformation was observed, as opposed to an extended conformation in the other. The CohB2 structures also displayed diverse conformations in their linker segments. In these structures, different linker conformations were observed in the individual molecules within the asymmetric unit of each structure. This conformational diversity implies that the linkers may adopt alternative conformations in their natural environment, consistent with varying environmental conditions. The findings suggest that linkers can play an important role in the assembly, dynamics and function of the cellulosomal components.

Original languageEnglish
Pages (from-to)86-97
Number of pages12
JournalJournal of Molecular Biology
Issue number1
StatePublished - 7 Aug 2009


FundersFunder number
United States-Israel Binational Science Foundation
Israel Science Foundation291/08, 159/07, 422/05


    • X-ray crystallography
    • linker segments
    • multienzyme complex
    • protein structure
    • scaffoldin


    Dive into the research topics of 'Intermodular Linker Flexibility Revealed from Crystal Structures of Adjacent Cellulosomal Cohesins of Acetivibrio cellulolyticus'. Together they form a unique fingerprint.

    Cite this