This is the sensor domain of sensor histidine kinase (AbfS) present in Cellvibrio japonicus. AbfS forms part of the AbfR/S two-component system which is needed to to activate the expression of the suite of enzymes that remove the numerous side chains from xylan. The overall fold of the sensor domain is that of a classical Per Arndt Sim domain [1]. This domain binds xylotriose and xylobiose (Matilla et.al, FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).

1: Regulation of the xylan-degrading apparatus of Cellvibrio japonicus by a novel two-component system. Emami K, Topakas E, Nagy T, Henshaw J, Jackson KA, Nelson KE, Mongodin EF, Murray JW, Lewis RJ, Gilbert HJ; J Biol Chem. 2009;284:1086-1096. PMID:18922794