3D domain swapping provides a minor alternative refolding pathway for ribonuclease A

The c-terminal β-hairpin of rnase a contains a turn with a cis asn113-pro114 peptide bond. pioneering pulsed hx experiments have shown that the c-terminal β-hairpin forms early during refolding. this is puzzling since the asn113-pro114 bond is predominately trans at this stage and this conformation destabilizes the native monomer. rnase a,when refolded at high concentration,forms a series of 3d domain-swapped oligomers. in the oligomers formed by cterminal -strand swapping,asn113-pro114 is trans and permits the formation of a new intersubunit -sheet. we hypothesize that oligomeric species with trans asn113-pro114 may form during refolding. such species could account for the hx results while comfortably accommodating asn113-pro114 in the trans conformation. here,we test this hypothesis by employing chromatographic methods to detect oligomers forming in refolding conditions and find significant amounts of dimer. we propose that a 3d domain-swapped dimeric intermediate provides a minor alternative pathway for rnase a refolding. copyright © 2011 bentham science publishers ltd.