Figure 4.

Top, HydF (pdb.id 5KH0) from T. melaniensis viewed from three angles (bottom of the cavity, and two views of the sides rotated 90° one relative to the other). To highlight the homodimeric assembly of the protein only one monomer has been colored according to secondary structure: in magenta the α-helices, in green the β-strands, the [4Fe-4S] cluster is in sphere representation. Bottom, reconstruction of the whole protein structure in the absence of GTP based on HydF from T. melaniensis (see text) including the missing amino-acid stretches. The left monomer has the reconstructed stretches colored in purple (switch 1 region) and dark orange (switch 2 region). The right monomer has been colored to highlight the three protein domains: GTPase domain in orange, dimerization domain in blue, and cluster-binding domain in green.