1gn4: Difference between revisions
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==Overview== | ==Overview== | ||
We have refined the X-ray structures of two site-directed mutants of the, iron-dependent superoxide dismutase (SOD) from Mycobacterium tuberculosis., These mutations which affect residue 145 in the enzyme (H145Q and H145E), were designed to alter its metal-ion specificity. This residue is either, Gln or His in homologous SOD enzymes and has previously been shown to play, a role in active-site interactions since its side-chain helps to, coordinate the metal ion via a solvent molecule which is thought to be a, hydroxide ion. The mutations were based on the observation that in the, closely homologous manganese dependent SOD from Mycobacterium leprae, the, only significant difference from the M. tuberculosis SOD within 10 A of, the metal-binding site is the substitution of Gln for His at ... | We have refined the X-ray structures of two site-directed mutants of the, iron-dependent superoxide dismutase (SOD) from Mycobacterium tuberculosis., These mutations which affect residue 145 in the enzyme (H145Q and H145E), were designed to alter its metal-ion specificity. This residue is either, Gln or His in homologous SOD enzymes and has previously been shown to play, a role in active-site interactions since its side-chain helps to, coordinate the metal ion via a solvent molecule which is thought to be a, hydroxide ion. The mutations were based on the observation that in the, closely homologous manganese dependent SOD from Mycobacterium leprae, the, only significant difference from the M. tuberculosis SOD within 10 A of, the metal-binding site is the substitution of Gln for His at position 145., Hence an H145Q mutant of the M. tuberculosis (TB) SOD was engineered to, investigate this residue's role in metal ion dependence and an isosteric, H145E mutant was also expressed. The X-ray structures of the H145Q and, H145E mutants have been solved at resolutions of 4.0 A and 2.5 A, respectively, confirming that neither mutation has any gross effects on, the conformation of the enzyme or the structure of the active site. The, residue substitutions are accommodated in the enzyme's three-dimensional, structure by small local conformational changes. Peroxide inhibition, experiments and atomic absorption spectroscopy establish surprisingly the, H145E mutant SOD has manganese bound to it whereas the H145Q mutant SOD, retains iron as the active-site metal. This alteration in metal, specificity may reflect on the preference of manganese ions for anionic, ligands. | ||
==About this Structure== | ==About this Structure== | ||
1GN4 is a | 1GN4 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis] with MN as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Superoxide_dismutase Superoxide dismutase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.15.1.1 1.15.1.1] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1GN4 OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: oxidoreductase]] | [[Category: oxidoreductase]] | ||
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Revision as of 15:35, 5 November 2007
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H145E MUTANT OF MYCOBACTERIUM TUBERCULOSIS IRON-SUPEROXIDE DISMUTASE.
OverviewOverview
We have refined the X-ray structures of two site-directed mutants of the, iron-dependent superoxide dismutase (SOD) from Mycobacterium tuberculosis., These mutations which affect residue 145 in the enzyme (H145Q and H145E), were designed to alter its metal-ion specificity. This residue is either, Gln or His in homologous SOD enzymes and has previously been shown to play, a role in active-site interactions since its side-chain helps to, coordinate the metal ion via a solvent molecule which is thought to be a, hydroxide ion. The mutations were based on the observation that in the, closely homologous manganese dependent SOD from Mycobacterium leprae, the, only significant difference from the M. tuberculosis SOD within 10 A of, the metal-binding site is the substitution of Gln for His at position 145., Hence an H145Q mutant of the M. tuberculosis (TB) SOD was engineered to, investigate this residue's role in metal ion dependence and an isosteric, H145E mutant was also expressed. The X-ray structures of the H145Q and, H145E mutants have been solved at resolutions of 4.0 A and 2.5 A, respectively, confirming that neither mutation has any gross effects on, the conformation of the enzyme or the structure of the active site. The, residue substitutions are accommodated in the enzyme's three-dimensional, structure by small local conformational changes. Peroxide inhibition, experiments and atomic absorption spectroscopy establish surprisingly the, H145E mutant SOD has manganese bound to it whereas the H145Q mutant SOD, retains iron as the active-site metal. This alteration in metal, specificity may reflect on the preference of manganese ions for anionic, ligands.
About this StructureAbout this Structure
1GN4 is a Single protein structure of sequence from Mycobacterium tuberculosis with MN as ligand. Active as Superoxide dismutase, with EC number 1.15.1.1 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Engineering a change in metal-ion specificity of the iron-dependent superoxide dismutase from Mycobacterium tuberculosis-- X-ray structure analysis of site-directed mutants., Bunting K, Cooper JB, Badasso MO, Tickle IJ, Newton M, Wood SP, Zhang Y, Young D, Eur J Biochem. 1998 Feb 1;251(3):795-803. PMID:9490054
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