Studies of macromolecular crowding

Diabetes, Digestive, Kidney Diseases

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Abstract

In last year's report we described a novel method for measuring the effect of volume excluding cosolutes on the kinetics of refolding of an enzymatically active protein. The method has been used to measure the refolding and reacquisition of enzymatic activity of carbonic anhydrase, a small single-subunit protein upon transfer from a solution containing 5 M GuHCl to 0.5 M GuHCl. Refolding experiments were carried out in buffer and in the presence of various concentrations (up to 150 g/L) of sucrose and Ficoll 70, a crosslinked polymer of sucrose. Increasing concentrations of sucrose and Ficoll accelerate the process of refolding but reduce the fraction of enzymatically active protein attained in the limit of long time. The results are interpreted in the context of a model in which unfolded protein can refold via parallel reactions to an enzymatically active state and a native-like but enzymatically inactive state, and that crowding by either sucrose or Ficoll accelerates folding to the inactive state more strongly than folding to the active state. A manuscript describing this work has been submitted for publication.