TCDB is operated by the Saier Lab Bioinformatics Group
TCIDNameDomainKingdom/PhylumProtein(s)
*9.A.39.1.1









Iron-regulated surface determinant, hemoglobin/myoglobin (but not hemopexin) receptor (IsdB) precursor (645 aas) (believed to extract heme iron and transport it into the cell). The path way for uptake of heme from human methemoglobin by the iron-regulated surface determinants (Isd) is: B(9.A.39.1.1)→ A(9.A.39.1.3)→ C(9.A.39.1.4)→ E(3.A.1.14.18)→ DF(3.A.1.14.18)→ cytoplasm (Zhu et al., 2008).
Bacteria
Firmicutes
IsdB of Staphylococcus aureus (Q6GHV7)
*9.A.39.1.2









Iron regulated surface determinant, Haptoglobin receptor A (HarA or IsdH) precursor (891 aas). Also binds hemoglobin and haptoglobin/hemoglobin complexes with nM or µM binding constants to an 8-stranded anti-parallel β-barrel domain (Dryla et al., 2007). The functionally distinct NEAT (NEAr Transporter) domain within IsdH extracts heme from methemoglobin (Pilpa et al., 2009). Hemoglobin/myoglobin receptor B (IsdB), transferrin, hemin, fetuin, asialofetuin receptor (IsdA), and the cell wall conduit, IsdC may comprise the full system (Villareal et al., 2008).

Bacteria
Firmicutes
IsdHABC of Staphylococcus aureus
IsdH (HarA) (Q931P4)
IsdA (P0C1S5)
IsdB (Q6GHV7)
IsdC (Q8KQR1)
*9.A.39.1.3









Iron-regulated surface determinant, IsdA (IsdA binds transferrin, heme, hemoglobin, hemin, fetuin, asialo fetuin, protein A, fibronectin and fibrinogen) (Liu et al., 2008). The pathway for uptake of heme from human methemoglobin by the iron-regulated surface determinants (Isd) is: B (9.A.39.1.1)→ A (9.A.39.1.3) → C (9.A.39.1.4) → E (3.A.1.14.18)→ DF (3.A.1.14.18) → cytoplasm (Zhu et al., 2008).

Bacteria
Firmicutes
IsdA of Staphylococcus aureus (354aas; 2TMSs at the N- and C-termini) (P0C1S5)
*9.A.39.1.4









Iron-regulated surface determinant, IsdC (interacts functionally with IsdA; Liu et al., 2008). The path way for uptake of heme from human methemoglobin by the iron-regulated surface determinants (Isd) is: B(9.A.39.1.1)→ A(9.A.39.1.3)→ C(9.A.39.1.4)→ E(3.A.1.14.18)→ DF(3.A.1.14.18)→ cytoplasm (Zhu et al., 2008). (227aas; 2TMSs at the N- and C- termini)

Bacteria
Firmicutes
IsdC of Staphylococcus aureus (Q8KQR1)
*9.A.39.1.5









Iron-regulated surface determinant (Isd) system: S-layer homologue domain protein (SHDP). IsdX1 and IsdX2 are hemophores that feed heme to IsdC surface protein (Fabian et al., 2009Tarlovsky et al., 2010).

Bacteria
Firmicutes
The IsdC/SHDP iron transporter of Bacillus anthracis 
IsdC (Q81L43)
SHDP (Q6EZT7) 
*9.A.39.1.6









SKN1 domain-containing protein of 364 aas and 2 TMSs

Bacteria
Firmicutes
SKN1 protein of Leuconostoc carnosum