Anti-sigma factor for SigI2. Negatively regulates SigI2 activity through direct interaction. Binding of the polysaccharide substrate to the extracellular C-terminal sensing domain of RsgI2 may induce a conformational change in its N-terminal cytoplasmic region, leading to the release and activation of SigI2. Interacts (via RsgI N-terminal anti-sigma domain) with SigI2.