This domain is found in maltosyltransferases, adopting a secondary structure that consists of eight antiparallel beta-strands forming an open-sided 'jelly roll' Greek key beta-barrel. Their exact function is, as yet, unknown [1].
Roujeinikova A, Raasch C, Burke J, Baker PJ, Liebl W, Rice DW.
The crystal structure of Thermotoga maritima maltosyltransferase and its implications for the molecular basis of the novel transfer specificity.
J. Mol. Biol. 312 119-31 2001
[PubMed: 11545590] http://dx.doi.org/10.1006/jmbi.2001.4944