1.15.1.2	evolution	based on the number of metal centres, superoxide reductases can be divided into two major subclasses: neelaredoxins (Nlr) solely contain the active site (1Fe-SOR), while desulfoferrodoxins (Dfx) harbour an additional rubredoxin-like iron centre (2Fe-SOR)	-, 746425	
1.15.1.2	evolution	Fe-SOR classification, detailed overview. One classification takes into consideration the primary and tertiary structures of SORs some enzymes contain only one Fe ion, but have a longer N-terminus with amino acid sequence and structural similarities with those of the respective domain of desulfoferrodoxins, but lacking the cysteine ligands to the desulforedoxin (Dfxs)-like center. According to the authors, SORs fall into three classes: classes I (Dfxs), II (neelaredoxins), and III (neelaredoxins structurally homologous to desulfoferrodoxins, with only one Fe center). In dendograms constructed from available amino acid sequences, class III enzymes cluster within the class I enzymes, it is plausible that class III SORs evolved from class I proteins by loss of the cysteine residues binding the desulforedoxin-like center, an event that may have occurred more than once because the Dfxs are not monophyletic. This classification misses the family of methanoferrodoxins. Another classification is based on the variability of N-terminal domains classifying SORs into seven classes. Class I or Dx-SOR includes the 2Fe-SORs, where the N-terminal is a desulforedoxin-like (Dx) domain. Class II includes the 1Fe-SORs that have no extra N-terminal domain. Class III SORs are analogous to Dx-SORs but lacking some or all of the Fe cysteine ligands (FeCys4) for the desulforedoxin-like Fe center and therefore lacking the FeCy4 site. Class IV includes SORs with an extra C-terminal domain containing an iron-sulfur center. The fifth class, termed HTH-Dx-SOR, includes Dx-SORs (2Fe-SOR) with an extended N-terminal helix-turn-helix domain present in transcription regulators. The sixth class, termed TAT-SOR, includes SORs from only a few organisms and the sequences are preceded by a putative twin-arginine signal peptide that suggests their periplasmic localization	-, 744687	
1.15.1.2	evolution	Giardia trophozoite expresses an enzyme probably acquired from a prokaryote by lateral gene transfer. Rubredoxins, small proteins with a [FeCys4] center known to be involved in electron transfer processes, are generally assumed to be the direct electron donors to SOR, based on the fact that the genes encoding rubredoxin and SOR lie in the same operon in some bacteria. Consistently, reduced rubredoxins are shown to reduce both 1Fe- and 2Fe-SORs, but physiological electron donors other than rubredoxins must exist because rubredoxins are missing in a large number of organisms that encode SORs	-, 727572	
1.15.1.2	evolution	the enzyme belongs to the class I superoxide reductase family	-, 726902	
1.15.1.2	evolution	the enzyme belongs to the class II superoxide reductase family	727313	
1.15.1.2	malfunction	mutation of two residues in the second coordination sphere of the SOR iron active site, K48 and I118, leads to the formation of a high-valent iron-oxo species when the mutant proteins are reacted with H2O2	-, 744022	
1.15.1.2	malfunction	the enzyme-inactivated 1754M strain is significantly more air-sensitive than the wild-type strain on NOS agarose plates exposed to air	-, 726989	
1.15.1.2	metabolism	the enzyme is involved in ROS detoxification	-, 746936	
1.15.1.2	additional information	activity remains essentially unchanged with change in the growth condition (maltose + peptides, maltose, maltose + peptides + sulfur S(0), maltose + sulfur S(0), peptides + sulfur S(0))	745202	
1.15.1.2	additional information	direct electron transfer measurements, in the presence of superoxide anion, overview	-, 726902