The crystal structure of the Bag6-BAG/Ubl4A-C heterodimer. (A) The overall structure of the Bag6-BAG/Ubl4A-C heterodimer in ribbon representation with Bag6-BAG shown in cyan and Ubl4A-C shown in magenta. Hydrophobic residues in Bag6 involved in packing are highlighted as orange sticks. (B) Sequence alignment of Bag6-BAG. D.mel, Drosophila melanogaster; D.rer, Danio rerio; H.sap, Homo sapiens; S.kow, Saccoglossus kowalevskii; T.cas, Tribolium castaneum; and X.tro, Xenopus tropicalis. The secondary structure based on the structure is highlighted above the text. The conserved hydrophobic and aromatic residues involved in the hydrophobic packing interactions between Bag6-BAG and Ubl4A-C are highlighted in orange. The extended Drosophila melanogaster sequence is a predicted protein sequence based on theoretical translation and may not reflect a physiological isoform.