Interaction of heat shock protein 90 B1 (Hsp90B1) with liposome reveals its potential role in protection the integrity of lipid membranes.

Heat shock proteins of 90kDa (Hsp90) are molecular chaperones essential for protein homeostasis. Besides chaperone activity, Hsp90 exhibits other cellular functions at membranes, yet how it interacts with membranes remains elusive. We report here that Hsp90B1 interacts with phospholipid membranes. We first cloned the full-length open reading frame of Hsp90B1 from Anas platyrhnchos (ApHsp90B1), and the gene was then heterologously expressed and purified. SPR analysis show the purified ApHsp90B1 interacts with phospholipid membranes with high affinity (KD 176±25nM), and the interaction occurs over a wide range of pH, which is especially distinct under acidic conditions. Tryptophan fluorescence and far-UV CD spectra studies find that the interaction of ApHsp90B1 with phospholipid membrane induces microenvironment changes of tryptophan residues and conformational change of some regions in ApHsp90B1, which might be the reason of its increased ATPase activity upon addition phospholipid vesicles. Importantly, the interaction of ApHsp90B1 with phospholipid vesicles significantly reduces lipolysis of the membrane phospholipid, suggesting that the interaction of Hsp90B1 with membrane could preserve membrane integrity. The present study therefore demonstrates for the first time that Hsp90B1 exhibits high affinity for phospholipid membrane and suggest Hsp90B1 play an important role in membrane-stabilizing via its interaction with membrane phospholipids.