Structural and functional modification of human serum albumin by lipid peroxidation by-products.

摘要

By-products of lipid peroxidation, specifically alpha,beta-unsaturated aldehydes, are known to modify nucleophilic amino acid residues, including lysine residues, in proteins. The produced alpha,beta-unsaturated aldehydes are stable enough to migrate from their site of origin, therefore allowing them to come in contact with a wide range of biomolecules in the system. Human serum albumin (HSA) is the most abundant plasma protein. It contains 58 lysine residues that are distributed throughout the sequence and tertiary structure of the protein, several of which are surface exposed. The research presented herein explores the possibility that HSA provides an outlet of consumption for the alpha,beta-unsaturated aldehydes thereby eliminating the harmful lipid peroxidation by-products from the system. The main objective of this research was to examine the structural and functional modifications of HSA when it acts as a potential "sink" for the lipid peroxidation by-products. Structural modifications were studied by investigating the susceptibility of HSA to be modified by alpha,beta-unsaturated aldehydes as characterized through time course experiments. The functional modifications were investigated through the impact of modified HSA to bind fatty acids or surrogate molecules. Additionally, isothermal titration calorimetry was used to determine if modification would compromise the ability of HSA to bind copper, therefore diminishing the antioxidant capacity of HSA by allowing an increase of free copper in the system. Results from these experiments will be discussed and conclusions made about the effect of modification on the structure and function of HSA.