InterPro domain: IPR036935

Ribosomal protein L9 is one of the proteins from the large ribosomal subunit.In Escherichia coli, L9 is known to bind directly to the 23S rRNA. It belongsto a family of ribosomal proteins grouped on the basis of sequence similarities [ 1 ].

The crystal structure of Bacillus stearothermophilus L9 shows the 149-residue protein comprises two globular domains connected by a rigid linker [ 2 ]. Each domain contains an rRNA binding site, and the protein functions as astructural protein in the large subunit of the ribosome. The C-terminal domain consists of two loops, an alpha-helix and a three-stranded mixedparallel, anti-parallel beta-sheet packed against the central alpha-helix. The long central alpha-helix is exposed to solvent in the middle and participates in thehydrophobic cores of the two domains at both ends.

1. Crystal structure of prokaryotic ribosomal protein L9: a bi-lobed RNA-binding protein. EMBO J. 13, 205-12
2. pH-dependent stability and folding kinetics of a protein with an unusual alpha-beta topology: the C-terminal domain of the ribosomal protein L9. J. Mol. Biol. 318, 571-82