Evidence for a self-associating equilibrium intermediate during folding of human growth hormone

摘要: It has been previously shown, by equilibrium denaturation, that human growth hormone (hGH) folds a cooperative two-state process. This is in contrast to the folding pathways of other nonhuman hormones contain stable monomeric and multimeric intermediates. We have reinvestigated denaturation hGH at higher protein concentrations found smooth transitions from native denatured state, but calculated free energy for unfolding, delta G, decreases with increasing concentration. The effect concentration on G unfolding due presence intermediates tendency self-associate. A correlation was between data observation precipitation occurs upon refolding, suggesting self-associated leads precipitation. Direct evidence existence soluble, associated intermediate obtained dynamic light scattering (DLS) analytical ultracentrifugation. Peptide fragments third helix either or bovine (bGH) were capable inhibiting formation this aggregated species prevent during refolding. show pathway similar except differences These findings are relevant design interpretation experiments, may be important understanding mechanistic details aggregation vivo.