Comparison of the Crystal Structures of the Human Manganese Superoxide Dismutase and the Homologous Aspergillus fumigatus Allergen at 2-Å Resolution

Abstract

Manganese superoxide dismutase (MnSOD) of Aspergillus fumigatus, a fungus involved in many pulmonary complications, has been identified as IgE-binding protein. It has been shown also that MnSODs from other organisms, including human, are recognized by IgE Abs from individuals sensitized to A. fumigatus MnSOD. Comparison of the fungal and the human crystal structure should allow the identification of structural similarities responsible for IgE-mediated cross-reactivity. The three-dimensional structure of A. fumigatus MnSOD has been determined at 2-Å resolution by x-ray diffraction analysis. Crystals belonged to space group P212121 with unit cell dimensions of a = 65.88 Å, b = 98.7 Å, and c = 139.28 Å. The structure was solved by molecular replacement using the structure of the human MnSOD as a search model. The final refined model included four chains of 199–200 amino acids, four manganese ions, and 745 water molecules, with a crystallographic R-factor of 19.4% and a free R-factor of 23.3%. Like MnSODs of other eukaryotic organisms, A. fumigatus MnSOD forms a homotetramer with the manganese ions coordinated by three histidines, one aspartic acid, and one water molecule. The fungal and the human MnSOD share high similarity on the level of both primary and tertiary structure. We identified conserved amino acids that are solvent exposed in the fungal and the human crystal structure and are therefore potentially involved in IgE-mediated cross-reactivity.

Purification, crystallization and X-ray structures of the two manganese superoxide dismutases fromCaenorhabditis elegans

“…Seven structures of MnSODs have been reported, three of which are tetrameric [human MnSOD (Borgstahl et al, 1992), Thermus thermophilus MnSOD (Ludwig et al, 1991) and Aspergillus fumigatus MnSOD (Fluckiger et al, 2002)], while the others are dimeric [Escherichia coli MnSOD (Edwards et al, 1998), Bacillus stearothermophilus MnSOD (Parker & Blake, 1988), Bacillus anthracis MnSOD (Boucher et al, 2005), Deinococcus radiodurans MnSOD (Dennis et al, 2006) and cyanobacterium MnSOD (Atzenhofer et al, 2002)]. All the structures share a common overall fold with the ironcontaining enzymes.…”

Cross-Reactivity and 1.4-Å Crystal Structure ofMalassezia sympodialisThioredoxin (Mala s 13), a Member of a New Pan-Allergen Family

“…Perhaps the most interesting class of pan-allergens includes environmental allergens sharing structural homology to self-Ags. These structures, including manganese superoxide dismutase, acidic ribosomal P 2 proteins, cyclophilins, and profilins (9,11,12,20,38), have been implicated in exacerbation and/or perpetuation of severe atopic disorders. In contrast to allergenicity, which is an intrinsic property of many different molecular structures, Ab-mediated cross-reactivity among homologous proteins is largely determined by common structural features shared between protein families (13).…”

“…These studies provide strong evidence for in vitro and in vivo humoral and cell-mediated IgE autoreactivity in patients suffering from long-lasting atopic diseases (8,11). Structural studies have shown that the availability of the crystal structure of a given allergen and its human homolog allows a detailed definition of the residues potentially involved in cross-reactivity (12). To date, the atomic details of the interaction between Ab and Ag are known for Ͼ30 Ab-Ag complexes (13).…”

Isolation and Identification of a Novel Mitochondrial Metalloprotease (PreP) That Degrades Targeting Presequences in Plants

“…In mitochondria, Hsp70 is localized to the matrix and drives mitochondrial import in an ATP-dependent manner (55). Mn-SOD has been identified in the matrix of mitochondria (53) and functions to neutralize produced oxygen radicals into H 2 O 2 (56). All the proteins identified by MALDI-TOF analysis are conserved, abundant mitochondrial proteins with a well characterized function.…”