Comparative analysis of Zur proteins from actinobacteria. (A), Multiple amino acid sequence alignment of actinobacterial Zur proteins, including FurB from M. tuberculosis H37Rv. The winged-helix DNA binding domain is highlighted in grey. Three zinc binding sites (Zn 1 to Zn 3) deduced from the crystal structure of the mycobacterial FurB protein  are specifically coloured. Zn 1 (yellow): Asp-71, Cys-85, His-91, and His-93; Zn 2 (red): Cys-96, Cys-99, Cys-136, and Cys-139; Zn 3 (blue): His-90, His-92, Glu-111, and His-128 (according to the C. glutamicum protein positions). (B), Maximum likelihood phylogenetic tree of Zur protein orthologues from actinobacteria. The source of the abbreviated Zur-like proteins is indicated by the respective GenBank identifiers.