Members of this family bind the chaperone SicP, which is required both to maintain the stability of SptP, as well as to ensure the eventual secretion of the protein. The domain is found in the Salmonella effector protein SptP, which interacts with SicP chaperone dimers mainly through four regions of its chaperone-binding domain. The structure of the SptP-SicP complex contains four molecules of SicP, aligned in a linear fashion and arranged in two sets of tightly bound homodimers that bind two SptP molecules. The SicP homodimers do not interact with each other, but are held together by a molecular interface formed between two SptP molecules. Each SptP molecule is wrapped around by three SicP chaperones (two chaperones from one homodimer and a third one from the opposite homodimer pair) [1].

1: Maintenance of an unfolded polypeptide by a cognate chaperone in bacterial type III secretion. Stebbins CE, Galan JE; Nature. 2001;414:77-81. PMID:11689946