Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.653864
Title: Bismuth recognition by proteins : implications for bismuth pharmacology
Author: Li, Hongyan
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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Abstract:
Transferrin is a bilobal glycoprotein with the function of transporting iron and other metal ions including diagnostic radioisotopes, therapeutic and toxic metal ions. A similar protein (ferric-ion-binding-protein) has also been found in several Gram-negative bacteria. An unexpectedly strong binding of Bi3+ (ionic radius 1.03Å) to the recombinant N-lobe of transferrin (hTF/2N) was found. The binding constant was calculated to be log K* 18.9± 0.2 at 310 K, 5 mM bicarbonate, 10 mM Hepes buffer at pH 7.4. This strong binding requires concomitant binding of a synergistic anion (carbonate) as proved by 13C NMR spectroscopy. Such a strong binding has led to the rationalization of the strength of metal binding to transferrin, which correlates well with metal acidity. Significantly this allowed the discovery of a new metal ion (Ti4+) binding to transferrin, which may be relevant to Ti4+ anticancer activity. 2D [1H, 13C] NMR spectra of recombinant e-13C-Met labeled transferrin at very low concentration were obtainable within a short time. The selectivity of lobe loading with Bi3+ is compared with that of other metal ions (Fe3+, Al3+ and Ga3+) and preferential loading to the C-lobe was found. Bi3+ induced similar chemical shift changes of Met residues as those induced by Fe3+, Al3+ and Ga3+ suggesting similar structural changes of the protein, probably from lobe-open to lobe-closed form although the local structure (Trp128 patch) may slightly different upon binding of different metal ions. A site specific mutant I132M with e-13C-Met labeled hTF/2N was used as a model to investigate possible target sites for bismuth in blood plasma. Using the chemical shift changes of Met residues as a probe, it was found that bismuth could be recognized by transferrin in the presence of large excess of albumin (biologically relevant conditions) and even in intact blood plasma. Albumin has been previously thought to be a potential target site for bismuth due to its free cysteine (Cys34). However, bismuth only associates weakly with albumin. For the first time, a direct detection of metallodrug binding to a protein at biologically relevant concentrations without separation was achieved.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.653864  DOI: Not available
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