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The binding of the B‐chain of ricin to Burkitt lymphoma cells
Author(s) -
Manevich Efim M.,
Tonevitsky Alexander G.,
Bergelson Lev D.
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80108-9
Subject(s) - ricin , fluorescence anisotropy , receptor , chemistry , ligand (biochemistry) , fluorescence , binding site , biophysics , binding constant , biochemistry , microbiology and biotechnology , biology , toxin , membrane , physics , quantum mechanics
It is shown that conformational changes of receptor proteins brought about by binding of a ligand induce changes in the lipid environment of the receptor that can be monitored by fluorescent lipid probes. On this basis a new approach to studies of ligand‐receptor binding is proposed. Using the interaction of the ricin B‐chain with Burkitt lymphoma cells as an example and fluorescent labelled sphingomyelin as a probe, the ligand‐induced changes of fluorescence anisotropy were shown to be concentration‐dependent and to permit determination of the binding constant and the number of receptor‐binding sites. The method was found to be specific and highly sensitive, allowing detection of the action of one R B molecule per cell. Scatchard analysis of the binding of 125 I‐R B demonstrated the presence on the cell surface of two binding sites with K d ~ 10 −10 and ~ 10 −8 M, respectively. Only the high‐affinity sites were detected by the fluorescence technique. Saturation of these sites resulted in maximum inhibition of protein synthesis.