Mechanistic investigation of domain specific unfolding of human serum albumin and the effect of sucrose

Abstract

This study is devoted to understand the unfoldingmechanismof amultidomain protein, human serum albumin (HSA), in absence and presence of the sucrose by steady-state and time-resolved fluorescence spectroscopy with domain specific marker molecules and is further being substantiated bymolecular dynamics (MD) simulation. In water, the domain III of HSA found to unfold first followed by domains I and II as the concentration of GnHCl is increased in themedium. The sequential unfolding behavior of different domains of HSA remains same in presence of sucrose; however, a higher GnHCl concentration is required for unfolding, suggesting stabilizing effect of sucrose on HSA. Domain I is found to bemost stabilized by sucrose. The stabilization of domain II is somewhat similar to domain I, but the effect of sucrose on domain III is found to be very small. MD simulation also predicted a similar behavior of sucrose on HSA. The stabilizing effect of sucrose is explained in terms of the entrapment of water molecules in between HSA surface and sucrose layer as well as direct interaction between HSA and sucrose. © 2013 The Protein Society.