Characterization of a prokaryotic haemerythrin from the methanotrophic bacterium Methylococcus capsulatus (Bath)

摘要: For a long time, the haemerythrin family of proteins was considered to be restricted only few phyla marine invertebrates. When analysing differential protein expression in methane-oxidizing bacterium, Methylococcus capsulatus (Bath), grown at high and low copper-to-biomass ratio, respectively, we identified putative prokaryotic expressed high-copper cultures. Haemerythrins are recognized by conserved sequence motif that provides five histidines two carboxylate ligands which coordinate iron atoms. The diiron site is located hydrophobic pocket capable binding O(2). We cloned M. gene it Escherichia coli as fusion with NusA. purified homogeneity cleaved from its partner. Recombinant (McHr) found fold into stable protein. Sequence similarity analysis all candidate residues involved (His22, His58, Glu62, His77, His81, His117, Asp122) amino acids forming O(2) may bind (Ile25, Phe59, Trp113, Leu114, Ile118). were also able model three-dimensional structure McHr maintaining correct positioning these residues. Furthermore, UV/vis spectrophotometric demonstrated presence conjugated atoms McHr. A comprehensive genomic database search revealed 21 different prokaryotes containing signature (PROSITE 00550), indicating haemerythrins subfamily.