This domain is found at the N-terminal of the chaperone SurA, a chaperone that assists correct folding of outer membrane proteins (OMPs) in Gram-negative bacteria [1]. This is the helical domain found at the N-terminal of SurA that, together with the C-terminal, forms a core domain which contains OMP binding sites. OMP binding induces conformational changes of SurA domains that protect OMPs from misfolding and aggregation [2]. The C-terminal of the SurA protein folds back and forms part of this domain also but is not included in the current alignment.

1: Crystallographic structure of SurA, a molecular chaperone that facilitates folding of outer membrane porins. Bitto E, McKay DB; Structure. 2002;10:1489-1498. PMID:12429090

2: Inter-domain dynamics in the chaperone SurA and multi-site binding to its outer membrane protein clients. Calabrese AN, Schiffrin B, Watson M, Karamanos TK, Walko M, Humes JR, Horne JE, White P, Wilson AJ, Kalli AC, Tuma R, Ashcroft AE, Brockwell DJ, Radford SE; Nat Commun. 2020;11:2155. PMID:32358557