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==Overview== | ==Overview== | ||
We have refined the X-ray structure of a site-directed G152A mutant of the, iron-dependent superoxide dismutase from Mycobacterium tuberculosis at 2.9, angstroms resolution. The mutation which replaces a glycine residue in a, surface loop with alanine was designed to alter the conformation of this, loop region which has previously been shown to play a crucial structural, role in quaternary interactions within the SOD tetramer. Gly-152 was, targeted as it has dihedral angles (phi = 83.1 degrees, psi = -0.3, degrees) close to the left-handed alpha-helical conformation which is, rarely adopted by other amino acids except asparagine. Gly-152 was, replaced by alanine as it has similar size and polarity, yet has a very, low tendency to adopt similar conformations. X-ray data collection on, ... | We have refined the X-ray structure of a site-directed G152A mutant of the, iron-dependent superoxide dismutase from Mycobacterium tuberculosis at 2.9, angstroms resolution. The mutation which replaces a glycine residue in a, surface loop with alanine was designed to alter the conformation of this, loop region which has previously been shown to play a crucial structural, role in quaternary interactions within the SOD tetramer. Gly-152 was, targeted as it has dihedral angles (phi = 83.1 degrees, psi = -0.3, degrees) close to the left-handed alpha-helical conformation which is, rarely adopted by other amino acids except asparagine. Gly-152 was, replaced by alanine as it has similar size and polarity, yet has a very, low tendency to adopt similar conformations. X-ray data collection on, crystals of this mutant at 2.9 angstroms resolution and subsequent, least-squares refinement to an R-value of 0.169 clearly establish that the, loop conformation is unaffected. Fluorescence studies of guanidine, hydrochloride denaturation establish that the mutant is 4 kcal/mol less, stable than the wild-type enzyme. Our results indicate that strict, conformational constraints imposed upon a region of polypeptide, due for, example to interactions with a neighbouring subunit, may force an alanine, residue to adopt this sterically hindered conformation with a consequent, reduction in stability of the folded conformation. | ||
==About this Structure== | ==About this Structure== | ||
1GN6 is a | 1GN6 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 FE 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=1GN6 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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G152A MUTANT OF MYCOBACTERIUM TUBERCULOSIS IRON-SUPEROXIDE DISMUTASE.
OverviewOverview
We have refined the X-ray structure of a site-directed G152A mutant of the, iron-dependent superoxide dismutase from Mycobacterium tuberculosis at 2.9, angstroms resolution. The mutation which replaces a glycine residue in a, surface loop with alanine was designed to alter the conformation of this, loop region which has previously been shown to play a crucial structural, role in quaternary interactions within the SOD tetramer. Gly-152 was, targeted as it has dihedral angles (phi = 83.1 degrees, psi = -0.3, degrees) close to the left-handed alpha-helical conformation which is, rarely adopted by other amino acids except asparagine. Gly-152 was, replaced by alanine as it has similar size and polarity, yet has a very, low tendency to adopt similar conformations. X-ray data collection on, crystals of this mutant at 2.9 angstroms resolution and subsequent, least-squares refinement to an R-value of 0.169 clearly establish that the, loop conformation is unaffected. Fluorescence studies of guanidine, hydrochloride denaturation establish that the mutant is 4 kcal/mol less, stable than the wild-type enzyme. Our results indicate that strict, conformational constraints imposed upon a region of polypeptide, due for, example to interactions with a neighbouring subunit, may force an alanine, residue to adopt this sterically hindered conformation with a consequent, reduction in stability of the folded conformation.
About this StructureAbout this Structure
1GN6 is a Single protein structure of sequence from Mycobacterium tuberculosis with FE 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
X-ray structure analysis of an engineered Fe-superoxide dismutase Gly-Ala mutant with significantly reduced stability to denaturant., Cooper JB, Saward S, Erskine PT, Badasso MO, Wood SP, Zhang Y, Young D, FEBS Lett. 1996 Jun 3;387(2-3):105-8. PMID:8674528
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