| TCID | Name | Domain | Kingdom/Phylum | Protein(s) | ||
|---|---|---|---|---|---|---|
|
1.N.3.1.1 | Hapless 2, HAP-2 of 705 aas and 2 TMSs, one N-terminal and one near the C-terminus. More TMSs giving hydrophobic peaks of lesser size may be present. Essential for pollen tube guidance, successful gamete attachment and fertilization (von Besser et al. 2006; Mori et al. 2006; Wong et al. 2010). | Eukaryota |
Viridiplantae, Streptophyta | HAP-2 of Arabidopsis thaliana (Mouse-ear cress) | ||
|
1.N.3.1.2 | HAP-2 of 952 aas with 2 or more TMSs (Steele and Dana 2009). | Eukaryota |
Metazoa, Porifera | HAP-2 of Amphimedon queenslandica (Sponge) | ||
|
1.N.3.1.3 | Male gamete fusion factor, HAP-2 of 742 aas and at least 2 TMSs. HAP2 is expressed in all seven mating types of T. thermophila and fertility is only blocked when the gene is deleted from both cells of a mating pair. HAP2 deletion strains of complementary mating types can recognize one another and form pairs, but pair stability is compromised and membrane pore formation at the nuclear exchange junction is blocked (Cole et al. 2014). Cole et al. 2014 proposed a model in which each of the several hundred membrane pores established at the conjugation junction of mating Tetrahymena represents the equivalent of a male/female interface, and that pore formation is driven on both sides of the junction by the presence of HAP2. | Eukaryota |
Ciliophora | HAP-2 of Tetrahymena thermophila | ||
|
1.N.3.1.4 | Uncharacterized protein of 821 aas and 2 TMSs. | Eukaryota |
UP of Vitrella brassicaformis
| |||
|
1.N.3.1.5 | HAP2-B-like isoform X2 protein of 708 aas and 2 TMSs. | Eukaryota |
Metazoa, Arthropoda | HAP2-B of Parasteatoda tepidariorum (House spider) (Achaearanea tepidariorum)
| ||
|
1.N.3.1.6 | Hapless 2, HAP2 or GCS1 of 1139 aas and 1 TMS. HAP2, an Arabidopsis sterility protein, localizes at the fusion site of Chlamydomonas minus gametes and mediates formation of tight prefusion membrane attachments with their respective gamete partners (Fédry et al. 2017). Membrane dye experiments show that HAP2 is essential for membrane merger (Liu et al. 2008). This protein may be essential for gamete fusion in animals, plants, fungi and protists (Ning et al. 2013). X-ray crystallographic studies reveal homology to class II viral membrane fusion proteins. Targeting the segment corresponding to the fusion loop by mutagenesis or by antibodies blocks gamete fusion (Fédry et al. 2017). | Eukaryota |
Viridiplantae, Chlorophyta | HAP2 of Chlamydomonas reinhardtii (Chlamydomonas smithii) | ||
|
1.N.3.1.7 | HAP2 of 812 aas and 1-3 TMSs. Functions in gamete fusion as does HAP2 in Chlamydomonas (TC# 1.N.3.6) (Liu et al. 2008; Fédry et al. 2017). | Eukaryota |
Apicomplexa | HAP2 of Plasmodium berghei |