PubMed · 6600116
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J E Burns. 1983. Equivalent half-value layers.. https://pubmed.ncbi.nlm.nih.gov/6600116/
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Human serum transferrin (hTF) is a single-chain bilobal glycoprotein (80 kDa) which transports Fe3+ and a variety of other metal ions in blood. Only diferric transferrin, not the apo-protein, binds strongly to transferrin receptors and is taken up by cells via receptor-mediated endocytosis. We show here that 2D [1H,13C] NMR studies of recombinant epsilon-[13C]Met-hTF allow the order of lobe loading with various metal ions, including Fe3+, to be determined. In particular, the resonance for Met-464, a residue in the hydrophobic patch of helix 5, is very sensitive to iron binding in the C-lobe. The selectivity of lobe loading with Fe3+ is compared to loading with Fe2+ (which binds as Fe3+), Al3+, Ga3+ and Bi3+. Similar changes in shifts of the Met residues are observed for these metal ions, suggesting that they induce similar conformational changes in the protein.
We isolated two yeast cDNA clones whose transcripts are induced by aluminum (Al) metal stress. Partial nucleotide sequencing showed that one is the HSP150 gene encoding a secreted heat shock protein, and the other corresponds to the SED1 gene encoding a putative membrane protein. To clarify the biological functions of these genes, we analyzed the sensitivity of gene-disrupted mutants to Al stress and to oxidative stresses. The Al tests indicated that the HSP150 protein served a basal protective role in Al stress, but SED1 did not; both of the genes had protective roles for oxidative stresses. The results for the HSP150 gene suggest that there is an overlap between Al ion stress, oxidative stress and heat shock stress in yeast.
Significant associations between the transferrin (TF) variant C2 and a number of disorders suspected to be caused by oxygen free radicals have been reported. Thus an increased frequency of the TFC2 variant has been found in patients with Alzheimer's disease (AD), and it has been hypothesized that AD is caused by free radical damage due to defective binding of iron and aluminium by TFC2. In a study of 64 patients with AD from northern Sweden we were able to confirm the association between TFC2 and AD, but there were no significant differences between TFC2 and other TF variants with respect to the binding of iron and aluminium.