PTP2 is a family of microsporidial polar-tube protein 2 sequences. Humans can be infected with the unicellular eukaryote Microsporidia which are obligate intracellular parasites that produce resistant spores. To initiate entry into a new host cell a unique motile process is formed by a sudden extrusion of the polar tube protein from the spore [1,2]. There are a series of conserved cysteine residues.

1: Reduction and expansion in microsporidian genome evolution: new insights from comparative genomics. Nakjang S, Williams TA, Heinz E, Watson AK, Foster PG, Sendra KM, Heaps SE, Hirt RP, Martin Embley T; Genome Biol Evol. 2013;5:2285-2303. PMID:24259309

2: Microsporidian invasion apparatus: identification of a novel polar tube protein and evidence for clustering of ptp1 and ptp2 genes in three Encephalitozoon species. Delbac F, Peuvel I, Metenier G, Peyretaillade E, Vivares CP; Infect Immun. 2001;69:1016-1024. PMID:11159998