The effect of the hexahistidine-tag in the oligomerization of HSC70 constructs

The hexahistidine is a fusion tag used for the isolation of proteins via an immobilized metal-ion affinity chromatography (IMAC). In the present study, we have purified and analyzed two constructs of the heat shock protein HSC70 in the presence or the absence of the His-tag (C30WT-His(+)/C30WT and C30 Delta L-His(+)/C30 Delta L). The oligomerization properties of the constructs were analyzed by size exclusion chromatography (SEC) and analytical ultracentrifugation (AU). Results from SEC analysis indicated that the His-tag promotes the dimerization of C30 Delta L-His(+) but has no effect on the elution profile of C30WT-His(+), compared to their respective untagged forms C30 Delta L and C30WT. These observations were also confirmed by AU analysis which indicates that C30 Delta L is stabilized in the dimeric form in the presence of the His-tag. These results emphasize the need to remove the His-tag before structural characterization of some recombinant proteins. (c) 2006 Elsevier B.V. All rights reserved.