The structure of this module is known [1] and consists of an Ig-like fold. The function of this domain is unknown, but might be involved in mediating interaction with carbohydrates.
Mosbah A, Belaich A, Bornet O, Belaich JP, Henrissat B, Darbon H.
Solution structure of the module X2 1 of unknown function of the cellulosomal scaffolding protein CipC of Clostridium cellulolyticum.
J. Mol. Biol. 304 201-17 2000
[PubMed: 11080456] http://dx.doi.org/10.1006/jmbi.2000.4192