Structure, stability, and flexibility of ribosomal protein L14e from Sulfolobus solfataricus.
Ribosomal protein L14e is a component of the large ribosomal subunit in both archaea and eukaryotes. We report here a high-resolution NMR solution structure of recombinant L14e and show that the N-terminal 57 residues adopt a classic SH3 fold. The protein contains a tight turn between strands 1 and 2 instead of the typical SH3 RT-loop, indicating that it is unlikely to interact with neighboring ribosomal proteins using the common SH3 site for proline-rich sequences. The remainder of the protein (39 residues) forms a largely extended chain with a short helix which packs onto the surface of the SH3 domain via hydrophobic interactions. It has the potential of adopting an alternative structure to expose a hydrophobic surface for protein-protein interactions in the ribosome without disruption of the SH3 fold. (15)N relaxation data demonstrate that the majority of the C-terminal chain is well-defined on the SH3 surface. The globular protein unfolds reversibly with a T(m) of 102.8 degrees C at pH 7, making it one of the most stable SH3 domain proteins described to date. The structure of L14e is expected to serve as a model for other members of the L14e family, along with members of the COG2163 group, including L6e and L27e. Interestingly, the N-terminal sequence of L14e shows the greatest similarity of any Sulfolobus protein to the reported N-terminal sequence of Sac8b, a DNA-binding protein reported by Grote et al. ((1986) Biochim. Biophys. Acta 873, 405-413). The likelihood that L14e and Sac8b are the same protein is discussed.
Alabama High Field NMR Laboratory, Department of Chemistry, University of Alabama in Huntsville, Huntsville, Alabama 35899, USA.
Stephen P
SP
Edmondson
Jacquelyn
J
Turri
Kelley
K
Smith
Andrew
A
Clark
John W
JW
Shriver
D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017510:Protein Folding; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000378:metabolism; D016415:Sequence Alignment; D048229:Sulfolobus solfataricus / Q000378:metabolism*; D013696:Temperature; D018909:src Homology Domains
D019843:Archaeal Proteins; D012269:Ribosomal Proteins; C041174:ribosomal protein L14