Indexed on: 27 Jul '01Published on: 27 Jul '01Published in: Protein Science
Transthyretin (TTR) subunits were labeled with a charge-modifying tag to evaluate the possibility of subunit exchange between tetramers under physiological conditions. Starting with a mixture of two TTR homotetramers, one having all subunits tagged at the N termini and the other composed of untagged subunits, heterotetramer formation as a function of time and temperature was evaluated using ion exchange chromatography. The data indicate that the subunit exchange can occur under native conditions at physiological pH in vitro, albeit slowly. Wild-type TTR exchanges subunits on a timescale of days at 37 degrees C and on a timescale of hours at 4 degrees C. The familial amyloid polyneuropathy-associated variant V30M exchanges subunits at the same rate as wild-type TTR at 4 degrees C but slower and less efficiently at 37 degrees C. Small molecule tetramer stabilizers abolish TTR subunit exchange, supporting a dissociative mechanism.