Alterations in the two globular domains or in the connecting alpha-helix of bacterial ribosomal protein L9 induces +1 frameshifts.
The ribosomal 50S subunit protein L9, encoded by the gene rplI, is an elongated protein with an alpha-helix connecting the N- and C-terminal globular domains. We isolated rplI mutants that suppress the +1 frameshift mutation hisC3072 in Salmonella enterica serovar Typhimurium. These mutants have amino acid substitutions in the N-terminal domain (G24D) or in the C-terminal domain (I94S, A102D, G126V, and F132S) of L9. In addition, different one-base deletions in rplI altered either the final portion of the C terminus or removed the C-terminal domain with or without the connecting alpha-helix. An alanine-to-proline substitution at position 59 (A59P), which breaks the alpha-helix between the globular domains, induced +1 frameshifting, suggesting that the geometrical relationship between the N and C domains is important to maintain the reading frame. Except for the alterations G126V in the C terminus and A59P in the connecting alpha-helix, our results confirm earlier results obtained by using the phage T4 gene 60-based system to monitor bypassing. The way rplI mutations suppress various frameshift mutations suggests that bypassing of many codons from several takeoff and landing sites occurred instead of a specific frameshift forward at overlapping codons.
Leipuviene
Ramune
R
Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden.
Björk
Glenn R
GR
D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D016368:Frameshift Mutation / Q000235:genetics*; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics*; D012485:Salmonella typhi / Q000235:genetics*
D001426:Bacterial Proteins; D012269:Ribosomal Proteins; C049650:ribosomal protein L9