ABSTRACT
Pyridoxal phosphate photoinactivates the peptidyltransferase activity of 50-S ribosomal subunits, LiCl split proteins and protein L16. Ethyromycin exhibits significant protection. These results, taken together with earlier reports, indicate the involvement of the single histidine of L16 in peptidyltransferase activity. The adjacent association in L16 of histidine and lysine indicates that pyridoxal phosphate should represent a selective inhibitor of peptidyltransferase activity.
Subject(s)
Acyltransferases/antagonists & inhibitors , Peptidyl Transferases/antagonists & inhibitors , Pyridoxal Phosphate/pharmacology , Ribosomal Proteins/metabolism , Ribosomes/enzymology , Chlorides , Dose-Response Relationship, Drug , Escherichia coli/enzymology , Histidine/metabolism , Kinetics , Light , Lithium , Lithium Chloride , Peptidyl Transferases/radiation effectsABSTRACT
Ethoxyformic anhydride abolishes the peptidyl transferase activity of 50-S ribosomal subunits, LiC1 split proteins and L16. Hydroxylamine treatment results in reactivation. Erythromycin exhibits significant protection with 50-S ribosomal subunits. With LiC1 split proteins and L16 significant protection was exhibited only after reconstitution. The results indicate that the ethoxyformic anhydride is reacting with approximately six histidines in LiC1 split proteins and one in L16. Since L16 has been reported to contain a single histidine, the results presented indicate the involvement of this histidine in peptidyl transferase activity.
Subject(s)
Acyltransferases/metabolism , Diethyl Pyrocarbonate/pharmacology , Formates/pharmacology , Peptidyl Transferases/metabolism , Ribosomal Proteins/metabolism , Ribosomes/enzymology , Bacterial Proteins/metabolism , Dinitrophenols/pharmacology , Erythromycin/pharmacology , Escherichia coli/drug effects , Escherichia coli/metabolism , Kinetics , Lithium/pharmacology , Ribosomes/drug effectsABSTRACT
The photochemical oxidation of the 50-S ribosomal subunit results in a rapid irreversible loss of peptidyl transferase activity. The first-order rate of inactivation occurring during the first forty minutes suggests that a single reactive group is being inactivation exhibits a maximum at pH 7.5. Erythromycin at a low concentration (0.04 mumol) affords significant protection. Puromycin also exerts a protective effect but at higher concentrations. Chloramphenicol, sparsomycin and lincomycin did not exert a protective effect. The loss in catalytic activity was not accompanied by a loss in substrate binding affinity of the donor and acceptor substrates.
