Unconventional mode of attachment of the Ruminococcus flavefaciens cellulosome to the cell surface

Marco T. Rincon, Tadej Čepeljnik, Jennifer C. Martin, Raphael Lamed, Yoav Barak, Edward A. Bayer, Harry J. Flint

Research output: Contribution to journalArticlepeer-review


Sequence extension of the scaffoldin gene cluster from Ruminococcus flavefaciens revealed a new gene (scaE) that encodes a protein with an N-terminal cohesin domain and a C terminus with a typical gram-positive anchoring signal for sortase-mediated attachment to the bacterial cell wall. The recombinant cohesin of ScaE was recovered after expression in Escherichia coli and was shown to bind to the C-terminal domain of the cellulosomal structural protein ScaB, as well as to three unknown polypeptides derived from native cellulose-bound Ruminococcus flavefaciens protein extracts. The ScaB C terminus includes a cryptic dockerin domain that is unusual in its sequence, and considerably larger than conventional dockerins. The ScaB dockerin binds to ScaE, suggesting that this interaction occurs through a novel cohesin-dockerin pairing. The novel ScaB dockerin was expressed as a xylanase fusion protein, which was shown to bind tenaciously and selectively to a recombinant form of the ScaE cohesin. Thus, ScaE appears to play a role in anchoring the cellulosomal complex to the bacterial cell envelope via its interaction with ScaB. This sortase-mediated mechanism for covalent cell-wall anchoring of the cellulosome in R. flavefaciens differs from those reported thus far for any other cellulosome system.

Original languageEnglish
Pages (from-to)7569-7578
Number of pages10
JournalJournal of Bacteriology
Issue number22
StatePublished - Nov 2005


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