8.A.147. The Peroxiredoxin Heme-binding Protein, Tpx1 (Tpx1) Family
Tpx1 is a peroxiredoxin that binds hemin and regulates the heme-iron/siderophore-iron transporter 3, Str3 (TC# 2.A.1.16.9). Tpx1 (Q74887; 192 aas and 0 - 2 possible TMSs), is a high affinity binding partner of Str3 (Normant et al. 2020). Under microaerobic conditions, cells deficient in heme biosynthesis and lacking the heme receptor Shu1 exhibit poor hemin-dependent growth in the absence of Tpx1, a cytoplasmic heme binding protein. Tpx1 exhibits an equilibrium constant value of 0.26 muM for hemin. The association of Tpx1 with hemin protects hemin from degradation by H2O2, and the peroxidase activity of hemin is lowered when it is bound to Tpx1 (Normant et al. 2020).