Structural Rearrangements in the Active Site of the Thermus thermophilus 16S rRNA Methyltransferase KsgA in a Binary Complex with 5'-Methylthioadenosine

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Journal of Molecular Biology

DOI:https://doi.org/10.1016/j.jmb.2009.02.066· OSTI ID:980530

Demirci, H; Belardinelli, R; Seri, E; Gregory, S; Gualerzi, C; Dahlberg, A; Jogl, G

Posttranscriptional modification of ribosomal RNA (rRNA) occurs in all kingdoms of life. The S-adenosyl-l-methionine-dependent methyltransferase KsgA introduces the most highly conserved rRNA modification, the dimethylation of A1518 and A1519 of 16S rRNA. Loss of this dimethylation confers resistance to the antibiotic kasugamycin. Here, we report biochemical studies and high-resolution crystal structures of KsgA from Thermus thermophilus. Methylation of 30S ribosomal subunits by T. thermophilus KsgA is more efficient at low concentrations of magnesium ions, suggesting that partially unfolded RNA is the preferred substrate. The overall structure is similar to that of other methyltransferases but contains an additional ?-helix in a novel N-terminal extension. Comparison of the apoenzyme with complex structures with 5?-methylthioadenosine or adenosine bound in the cofactor-binding site reveals novel features when compared with related enzymes. Several mobile loop regions that restrict access to the cofactor-binding site are observed. In addition, the orientation of residues in the substrate-binding site indicates that conformational changes are required for binding two adjacent residues of the substrate rRNA.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 980530
• Report Number(s): BNL--93448-2010-JA
• Journal Information: Journal of Molecular Biology, Journal Name: Journal of Molecular Biology Vol. 388; ISSN JMOBAK; ISSN 0022-2836
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ADENOSINE
ANTIBIOTICS
CONFORMATIONAL CHANGES
CRYSTAL STRUCTURE
ENZYMES
MAGNESIUM IONS
METHYLATION
MODIFICATIONS
ORIENTATION
RESIDUES
RIBOSOMAL RNA
RNA
SUBSTRATES
national synchrotron light source