This domain is found in large proline-rich protein BAG6 protein. It has a conserved SDL sequence motif. Human BAG6 is an ATP-independent molecular chaperone preventing the aggregation of misfolded and hydrophobic patches-containing proteins [1]. It functions as part of a cytosolic protein quality control complex, the BAG6/BAT3 complex, which maintains these client proteins in a soluble state and participates to their proper delivery to the endoplasmic reticulum or alternatively can promote their sorting to the proteasome where they undergo degradation [1, 2, 3, 4].

1: A ubiquitin ligase-associated chaperone holdase maintains polypeptides in soluble states for proteasome degradation. Wang Q, Liu Y, Soetandyo N, Baek K, Hegde R, Ye Y; Mol Cell. 2011;42:758-770. PMID:21636303

2: Bat3 promotes the membrane integration of tail-anchored proteins. Leznicki P, Clancy A, Schwappach B, High S; J Cell Sci. 2010;123:2170-2178. PMID:20516149

3: Protein targeting and degradation are coupled for elimination of mislocalized proteins. Hessa T, Sharma A, Mariappan M, Eshleman HD, Gutierrez E, Hegde RS; Nature. 2011;475:394-397. PMID:21743475

4: Mechanistic basis for a molecular triage reaction. Shao S, Rodrigo-Brenni MC, Kivlen MH, Hegde RS; Science. 2017;355:298-302. PMID:28104892