Transthyretin microheterogeneity and thyroxine binding are influenced by non-amino acid components and glutathione constituents.

Two non-amino acid components as well as the glutathione constituents in labile associations with transthyretin (TTR) have been detected by preparative polyacrylamide gel electrophoresis from preparations isolated by affinity chromatography on Sepharose-bound retinol-binding protein (RBP). Incubation of native or reduced TTR with these novel components influenced the quaternary structure and caused reactions with reduced TTR in particular. Reduction of isolated TTR monomers released cysteine from the quantitatively major monomer, but non-amino-acid components from another dominating monomer. The reaction patterns also influence thyroxine (T4) binding. These relationships indicate that interactions in serum of TTR with constituents of glutathione and components different from T4 and retinol-RBP are important for the metabolism and function of TTR.