1dtg
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HUMAN TRANSFERRIN N-LOBE MUTANT H249E
OverviewOverview
Serum transferrin is the major iron transport protein in humans. Its, function depends on its ability to bind iron with very high affinity, yet, to release this bound iron at the lower intracellular pH. Possible, explanations for the release of iron from transferrin at low pH include, protonation of a histidine ligand and the existence of a pH-sensitive, "trigger" involving a hydrogen-bonded pair of lysines in the N-lobe of, transferrin. We have determined the crystal structure of the His249Glu, mutant of the N-lobe half-molecule of human transferrin and compared its, iron-binding properties with those of the wild-type protein and other, mutants. The crystal structure, determined at 2.4 A resolution (R-factor, 19.8%, R(free) 29.4%), shows that Glu 249 is directly bound to iron, in, place of the His ligand, and that a local movement of Lys 296 has broken, the dilysine interaction. Despite the loss of this potentially, pH-sensitive interaction, the H249E mutant is only slightly more, acid-stable than wild-type and releases iron slightly faster. We conclude, that the loss of the dilysine interaction does make the protein more acid, stable but that this is counterbalanced by the replacement of a neutral, ligand (His) by a negatively charged one (Glu), thus disrupting the, electroneutrality of the binding site.
DiseaseDisease
Known diseases associated with this structure: Atransferrinemia OMIM:[190000], Iron deficiency anemia, susceptibility to OMIM:[190000]
About this StructureAbout this Structure
1DTG is a Single protein structure of sequence from Homo sapiens with FE and CO3 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Mutation of the iron ligand His 249 to Glu in the N-lobe of human transferrin abolishes the dilysine "trigger" but does not significantly affect iron release., MacGillivray RT, Bewley MC, Smith CA, He QY, Mason AB, Woodworth RC, Baker EN, Biochemistry. 2000 Feb 15;39(6):1211-6. PMID:10684598
Page seeded by OCA on Mon Nov 12 16:35:49 2007