title: Trp128Tyr mutation in the N-lobe of recombinant human serum transferrin: 1H- and 15N-NMR and metal binding studies.
abstract: The conserved Trp residue within helix 5 of the N-lobe of human serum transferrin (hTF/2N, 40 kDa) has been mutated to Tyr. NMR and CD spectra and energy calculations show that the mutation causes little perturbation of the overall structure of hTF/2N although the chelating agent Tiron removed Fe3+ from the mutant protein about three times faster than from wild-type hTF/2N. 1H-NMR resonances of residues in the Leu122-Trp128-Ile132 hydrophobic patch are assigned both by ring current calculations and with the aid of the mutation. [1H, 15N]-NMR resonances for 11 of the 14 Tyr residues were observed in the spectra of 15N-Tyr-hTF/2N and a resonance for Tyr128 was assignable in spectra of the mutant. The 15N resonance of Y128 was sensitive to oxalate and Ga3+ binding, and Ga3+ binding perturbed 15N resonances for most of the Tyr residues. Since these are well distributed over the N-lobe, it can be concluded that metal-induced structural changes are not merely local to the binding site.
authors.affiliation: Department of Chemistry, Birbeck College, University of London, UK.
authors.forename: E J
authors.initials: EJ
authors.lastname: Beatty
authors.forename: M C
authors.initials: MC
authors.lastname: Cox
authors.forename: T A
authors.initials: TA
authors.lastname: Frenkiel
authors.forename: Q Y
authors.initials: QY
authors.lastname: He
authors.forename: A B
authors.initials: AB
authors.lastname: Mason
authors.forename: P J
authors.initials: PJ
authors.lastname: Sadler
authors.forename: A
authors.initials: A
authors.lastname: Tucker
authors.forename: R C
authors.initials: RC
authors.lastname: Woodworth
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D001665:Binding Sites; D002942:Circular Dichroism; D006801:Humans; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014168:Transferrin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D011994:Recombinant Proteins; D014168:Transferrin; D014443:Tyrosine; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D014364:Tryptophan; D007501:Iron