Photoaffinity labeling of the pactamycin binding site on eubacterial ribosomes
- 1 July 1985
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 24 (14) , 3667-3672
- https://doi.org/10.1021/bi00335a040
Abstract
Pactamycin, an inhibitor of the initial steps of protein synthesis, has an acetophenone group in its chemical structure that makes the drug a potentially photoreactive molecule. In addition, the presence of a phenolic residue makes it easily suspectible to radioactive labeling. Through iodination, 1 radioactive derivative of pactamycin was obtained with biological activities similar to the unmodified drug when tested on in vivo and cell-free systems. With the use of [125I]iodopactamycin, ribosomes of Escherichia coli were photolabeled under conditions that preserve the activity of the particles and guarantee the specificity of the binding sites. Under these conditions, RNA is preferentially labeled when free, small ribosomal subunits are photolabeled, but proteins are the main target in the whole ribosome. An important conformational change apparently takes place in the binding site on association of the 2 subunits. The major labeled proteins are S2, S4, S18, S21 and L13. These proteins in the pactamycin binding site are probably related to the initiation step of protein synthesis.This publication has 15 references indexed in Scilit:
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