| TCID | Name | Domain | Kingdom/Phylum | Protein(s) |
|---|---|---|---|---|
|
2.A.112.1.1 | The human KX blood group antigen (putative amino acid transporter), KX antigen (Suzuki et al. 2013). | Eukaryota |
Metazoa, Chordata | The KX blood group antigen of Homo sapiens |
|
2.A.112.1.2 | Cell death abnormality protein 8; phospholipid flippase (in to out) (Suzuki et al. 2013; Chen et al. 2013). | Eukaryota |
Metazoa, Nematoda | ced-8 of Caenorhabditis elegans |
|
2.A.112.1.3 | The X Kell blood group precursor-related family member 8 homologue isoform CRAa of 401 aas (XK-related protein 8 or XkR8) (Suzuki et al. 2013). | Eukaryota |
Metazoa, Chordata | XkR8 of Mus musculus |
|
2.A.112.1.4 | Uncharacterized protein of 374 aas and ~ 10 TMSs | Eukaryota |
Metazoa, Arthropoda | UP of Culex quinquefasciatus (Southern house mosquito) (Culex pungens) |
|
2.A.112.1.5 | XkR8 homologue of 352 aas and 8 - 10 TMSs. | Eukaryota |
Metazoa, Arthropoda | XkR8 homologue of Drosophila melanogaster |
|
2.A.112.1.6 | The XK-related protein 2, XKP2 of 440 aas (Calenda et al. 2006). | Eukaryota |
Metazoa, Chordata | XKP2 of Homo sapiens |
|
2.A.112.1.7 | The XK-related protein 3, XKR3; XRG3, XTES of 459 aas (Calenda et al. 2006). | Eukaryota |
Metazoa, Chordata | XKR3 of Homo sapiens |
|
2.A.112.1.8 | XK protein 6 of 675 aas | Eukaryota |
Metazoa, Platyhelminthes | XK protein of Hymenolepis microstoma (Rodent tapeworm) (Rodentolepis microstoma) |
|
2.A.112.1.9 | Uncharacterized protein of 470 aas | Eukaryota |
Metazoa, Chordata | UP of Branchiostoma floridae (Florida lancelet) (Amphioxus) |
|
2.A.112.1.10 | Uncharacterized XK-related protein of 450 aas | Eukaryota |
Metazoa, Arthropoda | UP of Daphnia pulex (water flea) |
|
2.A.112.1.11 | Xkr4 of 650 aas and 10 TMSs in a 2 + 1 + 2 + 2 + 1 + 2 TMS arrangement, suggestive of a 5 TMS repeat unit. Xrk4 catalyzes phosphatidyl serine flipping from the inner leaflet to the outer leaflet of the cell membrane to signal appoptosis. It has a C-terminal caspase recognition signal that may play an important role. Xkr4, 8 and 9 have this activity and have several essential residues in TMS2 and cytoplasmic loop 2 (Suzuki et al. 2014). Xkr4 is activated by caspase-mediated cleavage and binding of the XRCC4 fragment. Zhang et al. 2023 showed that extracellular calcium is a factor needed to activate Xkr4. A constitutively active mutant of Xkr4 was found to induce phospholipid scrambling in an extracellular, but not intracellular, calcium-dependent manner. Other Xkr family members also require extracellular calcium for activation. D123 and D127 of TMS1 and E310 of TMS3 coordinate calcium binding, and the E310K mutation-mediated salt bridge between TMS1 and TMS3 bypasses the requirement for calcium. Disulfide bond formation between these two TMSs also activates phospholipid scrambling without calcium (Zhang et al. 2023). | Eukaryota |
Metazoa, Chordata | Xkr4 of Homo sapiens |
|
2.A.112.1.12 | Xkr9 of 650 aas. Catalyzes phosphatidyl serine flipping from the inner leaflet to the outer leaflet of the cell membrane to signal appoptosis. It has a C-terminal caspase recognition signal that may play an important role. Xkr4, 8 and 9 have this activity and have several essential residues in TMS2 and cytoplasmic loop 2 (Suzuki et al. 2014). | Eukaryota |
Metazoa, Chordata | Xkr9 of Homo sapiens |
|
2.A.112.1.13 | Xkr8 (XK8, XRG8) is of 395 aas and 6 - 11 apparent TMSs based on hydropathy plots. It catalyzes phosphatidyl serine (PS) flipping from the inner leaflet to the outer leaflet of the cell membrane to signal appoptosis (Sivagnanam et al. 2017). It has a C-terminal caspase recognition sequence that may play a role in apoptosis signalling. Xkr4 TC# 2.A.112.1.11), Xkr8 and Xkr9 (TC# 2.A.112.1.12) have this activity and have several essential residues in TMS2 and cytoplasmic loop 2 (Suzuki et al. 2014). It is a 6 TMS protein that is activated by caspases during apoptosis and promotes phospholipid scrambling, thus exposing PS as an "eat-me-signal" (Suzuki and Nagata 2014). Basigin (BSG; TC# 2.A.23.1.1) and neuroplastin (NPTN; TC# 2.A.23.1.8)) bind to Xkr8 and usher it to the plasma membrane (Suzuki et al. 2016). | Eukaryota |
Metazoa, Chordata | Xkr8 of Homo sapiens |
|
2.A.112.1.14 | XKR5 of 686 aas and 5 or 6 TMSs | Eukaryota |
Metazoa, Chordata | XKR5 of Homo sapiens |
|
2.A.112.1.15 | XK-related protein of 603 aas and 8 TMSs. | Eukaryota |
Metazoa, Annelida | XK-protein of Capitella teleta (Polychaete worm) |
|
2.A.112.1.16 | XK-like protein of 667 aas and 9 TMSs | Eukaryota |
Metazoa, Chordata | XK-like protein of Ciona intestinalis (Transparent sea squirt) (Ascidia intestinalis) |
|
2.A.112.1.17 | XK8 or XraB of 404 aas and 9 TMSs | Eukaryota |
Metazoa, Chordata | XK8 of Ciona intestinalis (Transparent sea squirt) (Ascidia intestinalis) |
|
2.A.112.2.1 | XkR8 homologue of 884 aas and 8 - 10 TMSs. | Eukaryota |
Viridiplantae, Chlorophyta | XkR8 homologue of Otreococcus lucimarinus |
|
2.A.112.2.2 | Uncharacterized protein of 1119 aas and 10 TMSs. | Eukaryota |
Viridiplantae, Chlorophyta | UP of Bathycoccus prasinos |
|
2.A.112.2.3 | Uncharacterized protein of 781 aas and 9 TMSs | Eukaryota |
Viridiplantae, Chlorophyta | UP of Coccomyxa subellipsoidea |
|
2.A.112.2.4 | Unchracterized protein of 892 aas | Eukaryota |
Viridiplantae, Chlorophyta | UP of Ostriococcus tauri |
|
2.A.112.4.1 | Uncharacterized protein of 652 aas and 8 TMSs | Eukaryota |
Metazoa, Arthropoda | UP of Drosophila grimshawi (Fruit fly) (Idiomyia grimshawi) |
|
2.A.112.4.2 | Uncharacterized protein of 694 aas and 9 TMSs. | Eukaryota |
Metazoa, Arthropoda | UP of Solenopsis invicta (Red imported fire ant) (Solenopsis wagneri) |
|
2.A.112.4.3 | Uncharacterized protein of 615 aas and 9 TMSs | Eukaryota |
Metazoa, Arthropoda | UP of Aedes aegypti (Yellowfever mosquito) (Culex aegypti) |