Structural Studies of the ATP-Binding Protein EttA from the Pathogenic Bacterium Staphylococcus aureus by Small-angle X-ray Scattering

ATPase EttA is the most common eubacterial protein of the ABC-F family, which facilitates the conformational transition of the ribosome from one state to another during elongation through a nucleotide-dependent interaction sensitive to the ATP/ADP ratio. Proteins of the ABC-F family confer resistance to antibiotics that bind in the peptidyltransferase center and the ribosomal tunnel; however, the details of the mechanism of action of this protein from Staphylococcus aureus are unclear. A comparison of the amino acid sequences of EttA proteins from S. aureus, Mycobacterium tuberculosis, and Escherichia coli indicates the presence of an additional 75 residues at the C-terminus of the protein, the function of which is unknown. The structure of the SaEttA protein was analyzed using small-angle X-ray scattering, which revealed a distinct domain arrangement and additional density at the C-terminus of the protein.