Type III secretion-associated chaperone required for SipB and SipC stabilization. Prevents premature association of SipB with SipC, which may lead to their targeting for degradation. Along with InvF, required for transcription activation of sigDE (sopB pipC), sicAsipBCDA, and sopE. Dimer or higher-order oligomers. Belongs to the LcrH/SycD chaperone family.