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A novel family of carbohydrate‐binding modules identified with Ruminococcus albus proteins
Author(s) -
Xu Qi,
Morrison Mark,
Nelson Karen E.,
Bayer Edward A.,
Atamof,
Lamed Raphael
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2004.04.005
Subject(s) - carbohydrate binding module , biochemistry , glycoside hydrolase , biology , cell wall , cellulosome , recombinant dna , chemistry , cellulose , enzyme , cellulase , clostridium thermocellum , gene
We recently showed that some of the enzymes underpinning cellulose solubilization by Ruminococcus albus 8 lack the conventional type of dockerin module characteristic of cellulosomal proteins and instead, bear an “X” domain of unknown function at their C‐termini. We have now subcloned and expressed six X domains and showed that five of them bind to xylan, chitin, microcrystalline and phosphoric‐acid swollen cellulose, as well as more heterogenous substrates such as alfalfa cell walls, banana stem and wheat straw. The X domain that did not bind to these substrates was derived from a family‐5 glycoside hydrolase (Cel5G), which possesses two X domains in tandem. Whereas the internal X domain failed to bind to the substrates, the recombinant dyad exhibited markedly enhanced binding relative to that observed for the C‐terminal X domain alone. The evidence supports a distinctive carbohydrate‐binding role of broad specificity for this type of domain, and we propose a novel family (designated family 37) of carbohydrate‐binding modules that appear to be peculiar to R. albus .