Secreted heme peroxidase from Dictyostelium discoideum: Insights into catalysis, structure, and biological role

Abstract

Oxidation of halides and thiocyanate by heme peroxidases to antimicrobial oxidants is an important cornerstone in the innate immune system of mammals. Interestingly, phylogenetic and physiological studies suggest that homologous peroxidases are already present in mycetozoan eukaryotes such as Dictyostelium discoideum. This social amoeba kills bacteria via phagocytosis for nutrient acquisition at its single-cell stage and for antibacterial defense at its multicellular stages. Here, we demonstrate that peroxidase A from D. discoideum (DdPoxA) is a stable, monomeric, glycosylated, and secreted heme peroxidase with homology to mammalian peroxidases. The first crystal structure (2.5 Å resolution) of a mycetozoan peroxidase of this superfamily shows the presence of a post-translationally-modified heme with one single covalent ester bond between the 1-methyl heme substituent and Glu-236. The metalloprotein follows the halogenation cycle, whereby compound I oxidizes iodide and thiocyanate at high rates (>108 m−1 s−1) and bromide at very low rates. It is demonstrated that DdPoxA is up-regulated and likely secreted at late multicellular development stages of D. discoideum when migrating slugs differentiate into fruiting bodies that contain persistent spores on top of a cellular stalk. Expression of DdPoxA is shown to restrict bacterial contamination of fruiting bodies. Structure and function of DdPoxA are compared with evolutionary-related mammalian peroxidases in the context of non-specific immune defense.

Structures of human dual oxidase 1 complex in low-calcium and high-calcium states

“…2). On the extracellular side of hDUOX1 resides the large N-terminal PHD domain which shares sequence homology with several peroxidases, such as peroxidase A from Dictyostelium discoideum (DdPoxA, PDB ID: 6ERC) 15 (Fig. S9a).…”

Diversification of AID/APOBEC-like deaminases in metazoa: multiplicity of clades and widespread roles in immunity

“…LODT01000051.1). In addition to three of the six secreted AADs from this organism, the locus also encodes two paralogous MAC-Perforin domain proteins (also showing gene expansions in slime molds) and a heme peroxidase, which has previously been implicated in antibacterial defense in slime molds ( 65 ). This supports the idea that secreted AADs might play a role in immunity more widely in eukaryotes.…”

Structure and mechanism of human dual oxidase 1 complex

“…Both CBS1 and CBS2 are evolutionary conserved in DUOX (Fig. S5) and DdPoxA 14 (Fig.S9c), indicating their functional importance. Interestingly, we found both CBS1 mutant (D397A+T332A) and CBS2 mutant (D109A+D174A) of DUOX1 failed to co-assemble with DUOXA1 (Fig.…”

“…hDUOX1 is the catalytic subunit of the complex (Fig.2). On the extracellular side of hDUOX1 resides the large N-terminal PHD domain which shares sequence homology with several peroxidases, such as peroxidase A from Dictyostelium discoideum (DdPoxA, PDB ID: 6ERC) 14 (Fig.S9a). Functional peroxidases utilize histidine-coordinated haem as the cofactor for catalysis.…”