Low affinity P_i or phosphate-zinc complex uptake transporter #1, PitA (K_m=2 μM) (Me·P_i:H⁺ symporter) (Beard et al. 2000; Jackson et al. 2008). Also transports tellurite (TeO₃^2-) slowly (Elías et al. 2012; Borghese et al. 2016).

Bacteria

PitA of E. coli (P0AFJ7)

Low affinity P_i transporter #2, PitB (K_m=30 μM) PitB, like PitA is also a Me·P_i:H⁺ symporter (Borghese et al. 2016)

Bacteria

PitB of E. coli

Probable low-affinity inorganic phosphate transporter, Pit

Pit of Mycobacterium bovis

Pit of Rhizobium meliloti

Putative low affinity P_i transporter PitH1, Sco4138 (Santos-Beneit et al. 2008).

Actinobacteria

PitH1 of Streptomyces coelicolor.

Putative low affinity P_i transporter PitH2, Sco1845 (Santos-Beneit et al., 2008).

Actinobacteria

PitH2 of Streptomyces coelicolor.

Low affinity inorganic phosphate uptake porter of 335 aas, PitA (Kim et al. 2014; Mechler L, ... Bertram R, personal communication).

Firmictues

PitA of Staphylococcus aureus

Phosphate:sodium symporter of 576 aas, Pho89 (Ahn et al. 2009).

Fungi

Pho89 of Komagataella pastoris (Yeast) (Pichia pastoris)

Phosphate transporter of 601 aas and 12 TMSs. Pho4.

Euglenozoa

Pho4 of Trypanosoma cruzi

Putative phosphate:sodium symporter of 752 aas and 12 - 14 TMSs.

PNaS family member of Lutibacter sp.

Putative sodium/phosphate symporter of 534 aas and 12 TMSs.

Na⁺:Phosphate symporter of Emiliania huxleyi virus 84

Phosphate uptake transporter of 869 aas and 10 TMSs, 6 N-terminal and 4 C-terminal. Toxoplasma expresses one Pi transporter harboring two  PHO4 binding domains (N- and C-terminal) that typify the PiT Family. This transporter named TgPiT, localizes to the plasma membrane, the inward buds of the endosomal organelles termed VAC, and many cytoplasmic vesicles (Asady et al. 2020). It catalyzes Pi:Na⁺ = 1:2 iselectrogenically. Upon Pi limitation in the medium, TgPiT is more abundant at the plasma membrane. ΔTgPiT parasites accumulate 4-times more acidocalcisomes, storage organelles for phosphate, and exhibit many traits that differ from the wild type organims including poor virulence (Asady et al. 2020). Either PgPiT or PT2 is essential for growth (Cui et al. 2022).

TgPiT of Toxoplasma gondii

Gibbon ape leukemia virus receptor 2/sodium-dependent phosphate uptake transporter, P_i:Na⁺ symporter, PiT2, PiT-2, GLVR2, SLC20A2. Mapping of the minimal transporting unit suggested a structure universal to all PiT-related proteins (Battger and Pedersen, 2011).The protein can transport P_i in the absence of Na⁺, and mutations allow Na⁺ transport in the absence of P_i. Transmembrane amino acids E(55) and E(575) appear to be responsible for linking P_i import to Na⁺symport (Bøttger et al. 2006). SLC20A2 variants cause the loss of Pi transport activity in mammalian cells (Sekine et al. 2019). Mutation of SLC20A2 seems to cause hereditary multiple exostoses (Li et al. 2020). It has been associated with Primary Familial Brain Calcification (PFBC) (Wang et al. 2012; Monfrini et al. 2023). Inorganic phosphate exporter heterozygosity in mice leads to brain vascular calcification, microangiopathy, and microgliosis (Maheshwari et al. 2023).

Animals

SLC20A2 of Homo sapiens

Low affinity housekeeping P_i transporter, PHT2, Pht2;1, Pht2,1, PT2-1 of 587 aas (Młodzińska and Zboińska 2016). The cucumber (Cucumis sativus) ortholog is involved in cucumber growth and metabolism; PT2-1 transcript levels in roots were high when grown in low (limiting) Pi-containing media, but low when grown in high Pi media (Naureen et al. 2018). Expressing Pht2;1 of Pteris vittata enhances phosphate transport in chloroplasts and increases arsenic tolerance in Arabidopsis thaliana (Feng et al. 2021).

Plants

Pht2;1 of Arabidopsis thaliana

The P_i:Na^₊ symporter, PfPit (669 aas; Saliba et al., 2006)

Malaria parasite

PfPit of Plasmodium falciparum (Q7YUD6)

The Pi:(Na⁺)₂ symporter, GLVR1, PiT1 or PiT-1 (Ravera et al., 2007). Mutating the conserved loop region between TMSs 2 and 3 alterred the binding properties of the transporter for Na⁺/Li⁺ and phosphate/arenate (Ravera et al. 2013).

Animals

Pit1 of Xenopus tropicalis (Q5BL44)

Na⁺-dependent phosphate transporter 1 (PiT-1). Gibbon ape leukemia virus receptor 1 (GLVR-1), Slc20A1 (K_M=24μM).  The protein has an experimentally tested 12 TMS topology (Farrell et al. 2009).  A knock-out mutation of the mouse orthologue results in abnormal endocytosis in the yolk sac visceral endoderm and embyonic death at the 12.5 day stage (Wallingford and Giachelli 2014). PiT1 levels are elevanted in somatotroph adenomas and are positively associated with tumor size, invasive behavior and tumor recurrence in somatotroph adenomas. It may be associated with the activation of the Wnt/betacatenin signaling pathway (Li et al. 2019).  The tails are important regulatory domains required for the endocytosis of the Rgt2 and Snf3 glucose sensing receptors triggered by different cellular stimuli (Xiao et al. 2024). Ehrlichia chaffeensis infects and proliferates inside monocytes and macrophages and causes human monocytic ehrlichiosis (HME), an emerging life-threatening tick-borne zoonosis. After internalization, E. chaffeensis resides in specialized membrane-bound inclusions, E. chaffeensis-containing vesicles (ECVs), to evade host cell innate immune responses and obtain nutrients (Li et al. 2024).  Host cells recognize E. chaffeensis Ech_1067, a penicillin-binding protein, and then upregulate the expression of PIT1, which transports phosphate from ECVs to the cytosol to inhibit bacterial growth.

Animals

SLC20A1 of Homo sapiens

Na⁺:Pi transporter, SPT1 (Li et al., 2011)

Plants

SPT1 of Dunaliella viridis (A7U4W2)

Low affinity high velocity phosphate transporter, PitA if 320 aas (McCarthy et al. 2014).

Crenarchaota

PitA of Metallosphaera cuprina

Low affinity phosphate transporter, PitA of 328 aas

Crenarchaota

PitA of Sulfolobus solfataricus

Low affinity phosphate carrier, PitA of 309 aas.

Euryarchaota

PitA of Archaeoglobus profundus

Sulfate:H⁺ symporter, CysP (Aguilar-Barajas et al., 2011; Mansilla and de Mendoza, 2000)

Bacteria

CysP (YlnA) of Bacillus subtilis