TY - JOUR
T1 - Reaction of ribosomal sulfhydryl groups with 5,5′-dithiobis(2-nitrobenzoic acid)
AU - Acharya, A. Seetharama
AU - Moore, P. B.
N1 - Funding Information:
We gratefully acknowledget he assistanceo f Mr Alan Senear, Mrs Adele Hack and Mrs Betty Rennie. We thank Dr F. M. Richards for his help in the preparation of the manuscript. This work was supported by a grant from the National Institutes of Health (AI-09167).
PY - 1973/5/15
Y1 - 1973/5/15
N2 - The number of sulfhydryl groups in the Escherichia coli ribosome has been measured by titration with 5,5′-dithiobis(2-nitrobenzoic acid). Under denaturing conditions, there are 38.8 ± 1.0 titratable thiols per 70 S ribosome and 22.8 ± 0.3 and 12.9 ± 0.3 titratable thiols per 50 S and 30 S subunits, respectively. Three categories of thiol groups can be distinguished in the native 70 S ribosome, a "fast reacting" class of about 3 residues, a "slow reacting" class of about 10 residues and a "buried" class including about 26 residues. The addition of polyuridylic acid to reaction mixtures protects a fast-reacting thiol in the 30 S subunit belonging to protein S1. The addition of urea to ribosome solutions makes the buried residues titratable. Denaturation occurs as a sharp transition at a urea concentration between 4 and 4.5 m. Urea does not fully dissociate the ribosome into RNA and protein. Instead, in the case of the 30 S subunit, a slowly sedimenting particle forms in the presence of urea, containing roughly 65% of the normal amount of protein.
AB - The number of sulfhydryl groups in the Escherichia coli ribosome has been measured by titration with 5,5′-dithiobis(2-nitrobenzoic acid). Under denaturing conditions, there are 38.8 ± 1.0 titratable thiols per 70 S ribosome and 22.8 ± 0.3 and 12.9 ± 0.3 titratable thiols per 50 S and 30 S subunits, respectively. Three categories of thiol groups can be distinguished in the native 70 S ribosome, a "fast reacting" class of about 3 residues, a "slow reacting" class of about 10 residues and a "buried" class including about 26 residues. The addition of polyuridylic acid to reaction mixtures protects a fast-reacting thiol in the 30 S subunit belonging to protein S1. The addition of urea to ribosome solutions makes the buried residues titratable. Denaturation occurs as a sharp transition at a urea concentration between 4 and 4.5 m. Urea does not fully dissociate the ribosome into RNA and protein. Instead, in the case of the 30 S subunit, a slowly sedimenting particle forms in the presence of urea, containing roughly 65% of the normal amount of protein.
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U2 - 10.1016/0022-2836(73)90385-9
DO - 10.1016/0022-2836(73)90385-9
M3 - Article
C2 - 4579545
AN - SCOPUS:0015925391
SN - 0022-2836
VL - 76
SP - 207
EP - 221
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 2
ER -