Peroxiredoxin

AhpC-TSA
Structure of AhpC, a bacterial 2-cysteine peroxiredoxin from Salmonella typhimurium.
Identifiers
Symbol	AhpC-TSA
Pfam	PF00578
Pfam clan	CL0172
InterPro	IPR000866
SCOP	1prx
SUPERFAMILY	1prx
OPM superfamily	139
OPM protein	1xvw
Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Peroxiredoxins (Prxs, EC 1.11.1.15; HGNC root symbol PRDX) are a ubiquitous family of antioxidant enzymes that also control cytokine-induced peroxide levels and thereby mediate signal transduction in mammalian cells. The family members in humans are PRDX1, PRDX2, PRDX3, PRDX4, PRDX5, and PRDX6. The physiological importance of peroxiredoxins is illustrated by their relative abundance (one of the most abundant proteins in erythrocytes after hemoglobin is peroxiredoxin 2).

Prxs were historically divided into three (mechanistic) classes:

The designation of “1-Cys” and “2-Cys” Prxs was introduced in 1994 as it was noticed that, among the 22 Prx sequences known at the time, only one Cys residue was absolutely conserved; this is the residue now recognized as the (required) peroxidatic cysteine, C_P. The second, semi-conserved cysteine noted at the time is the resolving cysteine, C_R, which forms an intersubunit disulfide bond with C_P in the widespread and abundant Prxs sometimes referred to as the “typical 2-Cys Prxs”. Ultimately it was realized that the C_R can reside in multiple positions in various Prx family members, leading to the addition of the “atypical 2-Cys Prx” category (Prxs for which a C_R is present, but not in the "typical," originally identified position).

With the large amount of information currently available regarding Prx structures and sequences, family members are now recognized to fall into six classes or subgroups, designated as Prx1 (essentially synonymous with “typical 2-Cys”), Prx5, Prx6, PrxQ, Tpx and AhpE groups. It is now recognized that the existence and location of C_R across all 6 groups is heterogeneous. Thus, even though the “1-Cys Prx” designation was originally associated with the Prx6 group based on the lack of a C_R in human PrxVI, and many Prx6 group members appear not to have a C_R, there are “1-Cys” members in all of the subgroups. Moreover, the C_R can be located in 5 (known) locations in the structure, yielding either an intersubunit or intrasubunit disulfide bond in the oxidized protein (depending on C_R location). To assist with identification of new members and the subgroup to which they belong, a searchable database (the PeroxiRedoxin classification indEX) including Prx sequences identified from GenBank (January 2008 through October 2011) was generated by bioinformatics analysis and is publicly available.