Phosphorylation of Ribosomal Protein L18 Is Required for Its Folding and Binding to 5S rRNA

Abstract

Ribosomal protein L18 from Bacillus stearothermophilus (bL18) includes a previously unreported phosphoserine residue. The folded conformation of the protein is stabilized by the dianionic form of the phosphate group of that residue. In the absence of Mg2+, the pK(a) of the phosphate group is so high that the protein is not fully folded at pH 7. In the presence of Mg2+, its pK(a) drops significantly, and consequently the native conformation of bL18 becomes stable at pH 7 and the protein is able to bind to 5S rRNA. Dephosphorylated bL18 does not bind to 5S rRNA at neutral pH.

Changes in Ribosome Function Induced by Protein Kinase Associated with Ribosomes of Streptomyces collinus Producing Kirromycin

“…From sedimentation analysis and 2-D gel electrophoresis it was clear that phosphorylation of L2, L3, L7, L16, L21, L24, and L27 had no effect on the integrity of 50S. This result is not surprising since, e.g., phosphorylation of L18 is required for its folding and binding to 5S RNA in Bacillus stearothermophilus (Bloemink and Moore, 1999) or differently phosphorylated protein S6 is bound to 40S subunits (Burkhard and Traugh, 1983). On the other hand, phosphorylation of 50S proteins influences subunit association to 70S ribosomes (Fig.…”

Comprehensive Analysis of Phosphorylated Proteins of Escherichia coli Ribosomes

“…In a recent high-throughput analysis of the steady-state phosphoproteome of E. coli , ribosomal proteins S7, L7/L12, L16, L19, and L28 were reported to be phosphorylated 16. Moreover, phosphorylation of L7/L12 and L18 in Thermus thermophilus and Bacillus stearothermophilus was reported previously 17,18. However, the knowledge of specific sites of phosphorylation of ribosomal proteins is still very incomplete, which significantly limits our ability to understand the regulation of prokaryotic protein synthesis by phosphorylation.…”

The Solution Structure of Ribosomal Protein L18 from Bacillus stearothermophilus

“…9 One hundred and nine of the expected 118 backbone amide cross-peaks in this spectrum have been assigned. Four of the missing resonances represent amides in the protein's N-terminal tail, another, which belongs to a residue at the start of an alpha helix, may be concealed by spectral overlap, and remaining four correspond to residues in the loops connecting the secondary structure elements of the protein's globular domain (see below).…”

“…The phage spectrum also includes strong cross-peaks at the chemical shifts assigned to A85 and A113, but they could BstL18 was purified as described. 9 15 N-labeled and 13 C/ 15 Nlabeled protein was produced from cells grown on Martek 9-N or Martek 9-CN medium (Spectra Stable Isotopes). Protein samples for NMR were dialyzed against 0.2 M NaCl, 20 mM PO 4 , 5 mM MgCl 2 (pH 6.0), their volumes reduced to 170 ml using a Centricon-3 concentrator, and made 10% in 2 H 2 O. NMR data were collected at 25 8C using a 600 MHz, Varian Unity Plus and a 500 MHz, Varian Unity wide bore spectrometer.…”