Unconventional mode of attachment of the Ruminococcus flavefaciens cellulosome to the cell surface.
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.
Rincon
Marco T
MT
Microbial Ecology Group, Rowett Research Institute, Aberdeen, UK. M.Rincon@rowett.ac.uk
Cepeljnik
Tadej
T
Martin
Jennifer C
JC
Lamed
Raphael
R
Barak
Yoav
Y
Bayer
Edward A
EA
Flint
Harry J
HJ
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics; D044603:Cellulosomes / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D045857:Ruminococcus / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D000097722:Cohesins
D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004269:DNA, Bacterial; D005656:Fungal Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D000097722:Cohesins; C422914:ScaB protein, Ruminococcus