This domain, which is predominantly found in archaeal alpha-amylases, adopts a secondary structure consisting of an eight-stranded antiparallel beta-sheet containing a Greek key motif. Its exact function has not, as yet, been determined [1].
Linden A, Mayans O, Meyer-Klaucke W, Antranikian G, Wilmanns M.
Differential regulation of a hyperthermophilic alpha-amylase with a novel (Ca,Zn) two-metal center by zinc.
J. Biol. Chem. 278 9875-84 2003
[PubMed: 12482867] http://dx.doi.org/10.1074/jbc.M211339200