Anti-sigma factor for SigI6. Negatively regulates SigI6 activity through direct interaction. Binding of the polysaccharide substrate to the extracellular C-terminal sensing domain of RsgI6 may induce a conformational change in its N-terminal cytoplasmic region, leading to the release and activation of SigI6 (By similarity). Binds to and hydrolyzes insoluble and soluble xylan substrates. Has low enzymatic activity (PubMed:20820855). Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Glycan degradation; xylan degradation. Interacts (via RsgI N-terminal anti-sigma domain) with SigI6. The GH10 domain binds to xylan. In the C-terminal section; belongs to the glycosyl hydrolase 10 (cellulase F) family.