1l5t: Difference between revisions
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==Overview== | ==Overview== | ||
Human lactoferrin is an iron-binding protein with a bilobal structure. | Human lactoferrin is an iron-binding protein with a bilobal structure. Each lobe contains a high-affinity binding site for a single Fe(3+) ion and an associated CO(3)(2-) ion. Although iron binds very tightly, it can be released at low pH, with an accompanying conformational change in which the two domains move apart. The Arg121Asp (R121D) mutant of the N-lobe half-molecule of human lactoferrin was constructed in order to test whether the Asp121 side chain could substitute for the CO(3)(2-) ion at the iron-binding site. The R121D mutant protein was crystallized in its apo form as it lost iron during crystallization. The crystals were also merohedrally twinned, with a twin fraction close to 0.5. Starting from the initial molecular-replacement solution [Breyer et al. (1999), Acta Cryst. D55, 129-138], the structure has been refined at 3.0 A resolution to an R factor of 13.9% (R(free) of 19.9%). Despite the moderate resolution, the high solvent content and non-crystallographic symmetry contributed to electron-density maps of excellent quality. Weakened iron binding by the R121D mutant is explained by occlusion of the anion-binding site by the Asp side chain. The opening of the two domains in the apoR121D structure (a rotation of 54 degrees ) closely matches that of the N-lobe in full-length lactoferrin, showing that the extent of the conformational change depends on properties inherent to the N-lobe. Differences in the C-terminal portion of the N-lobe (residues 321-332) for apoR121D relative to the closed wild-type iron-bound structure point to the importance of this region in stabilizing the open form. | ||
==Disease== | ==Disease== | ||
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[[Category: Homo sapiens]] | [[Category: Homo sapiens]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Anderson, B | [[Category: Anderson, B F.]] | ||
[[Category: Baker, E | [[Category: Baker, E N.]] | ||
[[Category: Breyer, W | [[Category: Breyer, W A.]] | ||
[[Category: Jameson, G | [[Category: Jameson, G B.]] | ||
[[Category: Tweedie, J | [[Category: Tweedie, J W.]] | ||
[[Category: glycoprotein]] | [[Category: glycoprotein]] | ||
[[Category: iron transport]] | [[Category: iron transport]] | ||
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[[Category: twinning]] | [[Category: twinning]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:41:40 2008'' | ||
Revision as of 14:41, 21 February 2008
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Crystal Structure of a Domain-Opened Mutant (R121D) of the Human Lactoferrin N-lobe Refined From a Merohedrally-Twinned Crystal Form.
OverviewOverview
Human lactoferrin is an iron-binding protein with a bilobal structure. Each lobe contains a high-affinity binding site for a single Fe(3+) ion and an associated CO(3)(2-) ion. Although iron binds very tightly, it can be released at low pH, with an accompanying conformational change in which the two domains move apart. The Arg121Asp (R121D) mutant of the N-lobe half-molecule of human lactoferrin was constructed in order to test whether the Asp121 side chain could substitute for the CO(3)(2-) ion at the iron-binding site. The R121D mutant protein was crystallized in its apo form as it lost iron during crystallization. The crystals were also merohedrally twinned, with a twin fraction close to 0.5. Starting from the initial molecular-replacement solution [Breyer et al. (1999), Acta Cryst. D55, 129-138], the structure has been refined at 3.0 A resolution to an R factor of 13.9% (R(free) of 19.9%). Despite the moderate resolution, the high solvent content and non-crystallographic symmetry contributed to electron-density maps of excellent quality. Weakened iron binding by the R121D mutant is explained by occlusion of the anion-binding site by the Asp side chain. The opening of the two domains in the apoR121D structure (a rotation of 54 degrees ) closely matches that of the N-lobe in full-length lactoferrin, showing that the extent of the conformational change depends on properties inherent to the N-lobe. Differences in the C-terminal portion of the N-lobe (residues 321-332) for apoR121D relative to the closed wild-type iron-bound structure point to the importance of this region in stabilizing the open form.
DiseaseDisease
Known disease associated with this structure: Deafness, autosomal dominant 1 OMIM:[602121]
About this StructureAbout this Structure
1L5T is a Single protein structure of sequence from Homo sapiens. Active as Diferric-transferrin reductase, with EC number 1.16.1.2 Full crystallographic information is available from OCA.
ReferenceReference
Structure of a domain-opened mutant (R121D) of the human lactoferrin N-lobe refined from a merohedrally twinned crystal form., Jameson GB, Anderson BF, Breyer WA, Day CL, Tweedie JW, Baker EN, Acta Crystallogr D Biol Crystallogr. 2002 Jun;58(Pt 6 Pt 2):955-62. Epub, 2002 May 29. PMID:12037297
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