Structural characterization of the ribosome maturation protein, RimM.

The RimM protein has been implicated in the maturation of the 30S ribosomal subunit. It binds to ribosomal protein S19, located in the head domain of the 30S subunit. Multiple sequence alignments predicted that RimM possesses two domains in its N- and C-terminal regions. In the present study, we have produced Thermus thermophilus RimM in both the full-length form (162 residues) and its N-terminal fragment, spanning residues 1 to 85, as soluble proteins in Escherichia coli and have performed structural analyses by nuclear magnetic resonance spectroscopy. Residues 1 to 80 of the RimM protein fold into a single structural domain adopting a six-stranded beta-barrel fold. On the other hand, the C-terminal region of RimM (residues 81 to 162) is partly folded in solution. Analyses of 1H-15N heteronuclear single quantum correlation spectra revealed that a wide range of residues in the C-terminal region, as well as the residues in the vicinity of a hydrophobic patch in the N-terminal domain, were dramatically affected upon complex formation with ribosomal protein S19.