Solution structure of the cysteine-rich domain of the Escherichia coli chaperone protein DnaJ

The solution structure of the cysteine-rich (CR) domain of Escherichia coli DnaJ has been solved by NMR methods. The structure of a 79 residue CR domain construct shows a novel fold with an overall V-shaped extended beta-hairpin topology. The CR domain is characterized by four C-X-X-C-X-G-X-G sequence motifs that bind two zinc ions. Residues in these two zinc modules show strong similarities in the grouping of resonances in the (15)N-(1)H HSQC spectrum and display pseudo-symmetry of the motifs in the calculated structures. The conformation of the cysteine residues coordinated to the zinc ion resembles that of the rubredoxin-knuckle, but there are significant differences in hydrogen bonding patterns in the two motifs. Zinc (15)N-(1)H HSQC titrations indicate that the fold of the isolated DnaJ CR domain is zinc-dependent and that one zinc module folds before the other. The C-X-X-C-X-G-X-G sequence motif is highly conserved in CR domains from a wide variety of species. The three-dimensional structure of the E. coli CR domain indicates that this sequence conservation is likely to result in a conserved structural motif.