Inhibition of Chloramphenicol Binding to Escherichia coli 70‐S Ribosomes by 2′(3′)‐O‐Aminoacyl‐dinucleoside Phosphates Derived from the Aminoacyl‐tRNA Acceptor Terminus

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Abstract
The effect of 2′ and 3′-O-aminoacyl-dinucleoside phosphates cytidylyl(3′-5′)-2′(3′)-O-l-phenylalanyladenosine (I), cytidylyl(3′-5′)-3′-deoxy-2′-O-l-phenylalanyladenosine (IIa), cytidylyl(3′-5′)-2′-deoxy-3′-O-l-phenylalanyladenosine (IIIa), cytidylyl(3′-5′)-3′-deoxy-2′-O-glycyladenosine (IIb), cytidylyl(3′-5′)-2′-deoxy-3′-O-glycyladenosine (IIIb), cytidylyl(3′-5′)-3′-deoxy-2′-O-l-leucyladenosine (IIc), cytidylyl(3′-5′)-2′-deoxy-3′-O-l-leucyladenosine (IIIc), cytidylyl(3′-5′)-3′-O-methyl-2′-O-l-phenylalanyladenosine (IId) and cytidylyl(3′-5′)-2′-O-methyl-3′-O-l-phenylalanyladenosine (IIId) as analogs of the 2′(3′)-aminoacyl-tRNA termini, on chloramphenicol binding to 70-S Escherichia coli ribosomes was investigated. The association constants (Kb) of the investigated compounds were determined by the equilibrium dialysis method. Based on the constancy of Kb over the range of inhibitor concentration, it was determined that the binding site of the 2′ isomers IIa–IIc overlaps with the chloramphenicol site, whereas the variability of Kb for the 3′ isomers IIIb, IIIc and especially IIIa seems to indicate that they do not achieve a complete fit. The consistently higher values of the Kb values for the 3′ isomers IIIa–IIIc relative to that of the 2′ isomers IIa–IIc also indicate a stabilization of the binding of the former due to a specific interaction between its amino acid portion and a ribosomal site.

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