1em1 | pdb_00001em1
X-RAY CRYSTAL STRUCTURE FOR HUMAN MANGANESE SUPEROXIDE DISMUTASE, Q143A
Structural highlights
Disease[SODM_HUMAN] Genetic variation in SOD2 is associated with susceptibility to microvascular complications of diabetes type 6 (MVCD6) [MIM:612634]. These are pathological conditions that develop in numerous tissues and organs as a consequence of diabetes mellitus. They include diabetic retinopathy, diabetic nephropathy leading to end-stage renal disease, and diabetic neuropathy. Diabetic retinopathy remains the major cause of new-onset blindness among diabetic adults. It is characterized by vascular permeability and increased tissue ischemia and angiogenesis. Function[SODM_HUMAN] Destroys superoxide anion radicals which are normally produced within the cells and which are toxic to biological systems.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedGlutamine 143 in human manganese superoxide dismutase (MnSOD) forms a hydrogen bond with the manganese-bound solvent molecule and is investigated by replacement using site-specific mutagenesis. Crystal structures showed that the replacement of Gln 143 with Ala made no significant change in the overall structure of the mutant enzyme. Two new water molecules in Q143A MnSOD were situated in positions nearly identical with the Oepsilon1 and Nepsilon2 of the replaced Gln 143 side chain and maintained a hydrogen-bonded network connecting the manganese-bound solvent molecule to other residues in the active site. However, their presence could not sustain the stability and activity of the enzyme; the main unfolding transition of Q143A was decreased 16 degrees C and its catalysis decreased 250-fold to k(cat)/K(m) = 3 x 10(6) M(-)(1) s(-)(1), as determined by stopped-flow spectrophotometry and pulse radiolysis. The mutant Q143A MnSOD and other mutants at position 143 showed very low levels of product inhibition and favored Mn(II)SOD in the resting state, whereas the wild type showed strong product inhibition and favored Mn(III)SOD. However, these differences did not affect the rate constant for dissociation of the product-inhibited complex in Q143A MnSOD which was determined from a characteristic absorbance at 420 nm and was comparable in magnitude ( approximately 100 s(-)(1)) to that of the wild-type enzyme. Hence, Gln 143, which is necessary for maximal activity in superoxide dismutation, appears to have no role in stabilization and dissociation of the product-inhibited complex. Multiple replacements of glutamine 143 in human manganese superoxide dismutase: effects on structure, stability, and catalysis.,Leveque VJ, Stroupe ME, Lepock JR, Cabelli DE, Tainer JA, Nick HS, Silverman DN Biochemistry. 2000 Jun 20;39(24):7131-7. PMID:10852710[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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