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Functional topography of human ribosomes as studied by affinity labeling with reactive mRNA analogs
G G Karpova1, D M Graifer, A A Malygin
1Institute of Bioorganic Chemistry, Siberian Division of the Russian Academy of Sciences, Novosibirsk.
Abstract:
Derivatives of 5'-32P labeled (pU)3 an (pU)6 bearing 4-(N-2-chloroethyl-N-methylamino)benzylmethylamine residue attached to 5'-phosphate via phosphamide bond and (Up)5U[32P]pC and (Up)11U[32P]pC bearing 4-(N-2-chloroethyl-N-methylamino)benzyl residue attached to 3'-end via benzylidene bond were applied for the affinity labeling of 80S ribosomes from human placenta in the presence of a cognate tRNA. The derivatives of 32P-labeled pAUG and pAUGU3 analogous to the 5'-phosphamides of (pU)n were used for affinity labeling of 40S subunits in the presence of ternary complex eIF-2.GTP.Met-tRNA(f). The sites of the reagents' attachment to 18S ribosomal RNA were identified by blot-hybridization of the modified 18S rRNA with restriction fragments of the corresponding rDNA. They were found to be located within positions 976-1057 for (pU)6 and pAUGU3 derivatives and within 976-1164 for (pU)3 and pAUG ones. The sites of 18S rRNA modification with the derivatives of (Up)5UpC and (Up)11UpC were found within positions 1610-1869 at 3'-end of the molecule. All the sites identified here are located presumably within highly conserved parts of the eukaryotic small subunit rRNA secondary structure.
Insights
Researchers used modified nucleotide probes to label human placental ribosomes, identifying specific binding sites on 18S ribosomal RNA. These sites are located in conserved regions of the small ribosomal subunit, crucial for protein synthesis.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Ribosomes are essential for protein synthesis, translating genetic information into proteins.
- Understanding ribosome structure and function is key to deciphering cellular processes and diseases.
- Affinity labeling is a powerful technique to map molecular interactions within complex cellular machinery.
Purpose of the Study:
- To identify specific binding sites of modified nucleotide derivatives on human 80S and 40S ribosomal subunits.
- To determine the precise locations of these binding sites on the 18S ribosomal RNA (rRNA).
- To investigate the structural context of these modification sites within the eukaryotic small subunit rRNA.
Main Methods:
- Affinity labeling of 80S ribosomes and 40S subunits using 32P-labeled nucleotide derivatives with specific chemical modifications.
- Identification of modification sites on 18S rRNA through blot-hybridization with restriction fragments of rDNA.
- Analysis of modification site locations within the 18S rRNA sequence and secondary structure.
Main Results:
- Specific regions on the 18S rRNA were identified as attachment sites for the affinity labeling reagents.
- Derivatives of (pU)6 and pAUGU3 labeled sites within positions 976-1057 of the 18S rRNA.
- Derivatives of (pU)3 and pAUG labeled sites within positions 976-1164, while (Up)5UpC and (Up)11UpC derivatives modified sites at the 3'-end (1610-1869).
Conclusions:
- The identified modification sites on 18S rRNA are likely located in highly conserved regions of the eukaryotic small subunit rRNA secondary structure.
- These findings provide insights into the structural organization of the ribosome and potential functional roles of these rRNA regions.
- The study contributes to a deeper understanding of ribosome-rRNA interactions and their implications in translation.