Placement of the alpha-sarcin loop within the 50S subunit: evidence derived using a photolabile oligodeoxynucleotide probe.
We report the synthesis of a radioactive, photolabile oligodeoxyribonucleotide probe and its exploitation in identifying 50S ribosomal subunit components neighboring the alpha-sarcin loop. The probe is complementary to 23S rRNA nt 2653-2674. Photolysis of the complex formed between the probe and 50S subunits leads to site-specific probe photoincorporation into proteins L2, the most highly labeled protein, L1, L15, L16 and L27, labeled to intermediate extents, and L5, L9, L17 and L24, each labeled to a minor extent. Portions of each of these proteins thus lie within 23 A of nt U2653. These results lead us to conclude that the alpha-sarcin loop is located at the base of the L1 projection within the 50S subunit. Such placement, near the peptidyl transferase center, provides a rationale for the extreme sensitivity of ribosomal function to cleavage of the alpha-sarcin loop.
Muralikrishna
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P
Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
Alexander
R W
RW
Cooperman
B S
BS
D000345:Affinity Labels; D001386:Azides / Q000378:metabolism; D001665:Binding Sites; D018076:DNA, Complementary / Q000378:metabolism; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins; D005816:Genetic Complementation Test; D007553:Isotope Labeling; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D012335:RNA, Ribosomal / Q000378:metabolism*; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism*
D000345:Affinity Labels; D001386:Azides; D018076:DNA, Complementary; D005656:Fungal Proteins; D015345:Oligonucleotide Probes; D010761:Phosphorus Radioisotopes; D012335:RNA, Ribosomal; D012338:RNA, Ribosomal, 23S; C014801:alpha-sarcin; C029534:hydroxysuccinimidyl-4-azidobenzoate; D004722:Endoribonucleases