Protonation and anion binding control the kinetics of iron release from human transferrin.
Summary of "Protonation and anion binding control the kinetics of iron release from human transferrin."
Iron release in vitro from human serum diferric transferrin (hFe(2)Tf) in acidic media (4.2 ≤ pH ≤ 5.4) in the presence of nonsynergistic anions occurs in at least five kinetic steps. Step 1 (most rapid) involves proton assisted release of carbonate from the protein. In subsequent steps, iron release from both the N- and C-terminal lobes is controlled by slow proton transfers and anion binding. In step 2, the N-terminal lobe takes up one proton with kinetic linkage to the binding of one anion. In step 3, iron release from the anion-linked N-terminal lobe is controlled by slow uptake of two protons with rate-constant, k(2N), of 2.6(6) × 10(7), 6.1(6) × 10(7), and 9(1) × 10(7) M(-2) s(-1) in the presence of Cl(-), NO(3)(-), and SO(4)(2-), respectively. In step 4, the C-terminal lobe takes up one proton with kinetic linkage to the binding of one anion. In step 5, iron release from the anion-linked C-terminal lobe is controlled by slow uptake of two protons with rate-constant, k(2C), of 8.4(2) × 10(4), 4.4(6) × 10(5), and 8.1(2) × 10(5) M(-2) s(-1) in the presence of Cl(-), NO(3)(-), and SO(4)(2-), respectively.
Affiliation
Department of Biochemistry and Molecular Biology and the Centre for Blood Research, Life Sciences Centre, 2350 Health Sciences Mall, University of British Columbia , Vancouver, BC V6T 1Z3 Canada.
Journal Details
This article was published in the following journal.
Name: The journal of physical chemistry. B
ISSN: 1520-5207
Pages: 3795-807
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22364386
- DOI: http://dx.doi.org/10.1021/jp205879h
Medical and Biotech [MESH] Definitions
Iron Regulatory Protein 1
A multifunctional iron-sulfur protein that is both an iron regulatory protein and cytoplasmic form of aconitate hydratase. It binds to iron regulatory elements found on mRNAs involved in iron metabolism and regulates their translation. Its RNA binding ability and its aconitate hydrolase activity are dependent upon availability of IRON.
Anemia, Iron-deficiency
Anemia characterized by decreased or absent iron stores, low serum iron concentration, low transferrin saturation, and low hemoglobin concentration or hematocrit value. The erythrocytes are hypochromic and microcytic and the iron binding capacity is increased.
Iron, Dietary
Iron or iron compounds used in foods or as food. Dietary iron is important in oxygen transport and the synthesis of the iron-porphyrin proteins hemoglobin, myoglobin, cytochromes, and cytochrome oxidase. Insufficient amounts of dietary iron can lead to iron-deficiency anemia.
Iron Chelating Agents
Organic chemicals that form two or more coordination links with an iron ion. Once coordination has occurred, the complex formed is called a chelate. The iron-binding porphyrin group of hemoglobin is an example of a metal chelate found in biological systems.
Iron Regulatory Protein 2
A multifunctional iron-sulfur protein that is both an iron regulatory protein and cytoplasmic form of aconitate hydratase. It binds to iron regulatory elements found on mRNAs involved in iron metabolism and regulates their translation. Its rate of degradation is increased in the presence of IRON.
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