Denatured states of human carbonic anhydrase II: an NMR study of hydrogen/deuterium exchange at tryptophan‐indole‐HNsites

Hydrogen/deuterium (H/D) exchange measurements in low and moderate concentrations of GuHCl were conducted on the side chain HNatoms of the seven tryptophans of pseudo wild‐type human carbonic anhydrase II. Tryptophans 5, 16 and 245, situated in or close to the N‐terminal domain were found to have little protection against exchange. The H/D exchange results for Trp‐123, Trp‐192 and Trp‐209 showed that a previously identified molten globule and the native state gave a similar protection against exchange. Global unfolding of the protein is necessary for the efficient exchange at Trp‐97, which is located in the central part of the β‐sheet.