Solution structure of the His12 -> Cys mutant of the N-terminal zinc binding domain of HIV-1 integrase complexed to cadmium

The solution structure of His12 --> Cys mutant of the N-terminal zinc bindi ng domain (residues 1-55; IN1-55) of HIV-1 integrase complexed to cadmium h as been solved by multidimensional heteronuclear NMR spectroscopy. The over all structure is very similar to that of the wild-type N-terminal domain co mplexed to zinc. In contrast to the wild-type domain, however, which exists in two interconverting conformational states arising from different modes of coordination of the two histidine side chains to the metal, the cadmium complex of the His12 --> Cys mutant exists in only a single form at low pH. The conformation of the polypeptide chain encompassing residues 10-18 is i ntermediate between the two forms of the wild-type complex.