Trophinin and tastin form a cell adhesion molecule complex that potentially mediates an initial attachment of the blastocyst to uterine epithelial cells at the time of implantation. Trophinin and tastin bind to an intermediary cytoplasmic protein called bystin. Bystin may be involved in implantation and trophoblast invasion because bystin is found with trophinin and tastin in the cells at human implantation sites and also in the intermediate trophoblasts at invasion front in the placenta from early pregnancy [1]. This family also includes the yeast protein ENP1. ENP1 is an essential protein in Saccharomyces cerevisiae and is localised in the nucleus [2]. It is thought that ENP1 plays a direct role in the early steps of rRNA processing as enp1 defective yeast cannot synthesise 20S pre-rRNA and hence 18S rRNA, which leads to reduced formation of 40S ribosomal subunits [3].

1: A cytoplasmic protein, bystin, interacts with trophinin, tastin, and cytokeratin and may be involved in trophinin-mediated cell adhesion between trophoblast and endometrial epithelial cells. Suzuki N, Zara J, Sato T, Ong E, Bakhiet N, Oshima RG, Watson KL, Fukuda MN; Proc Natl Acad Sci U S A 1998;95:5027-5032. PMID:9560222

2: ENP1, an essential gene encoding a nuclear protein that is highly conserved from yeast to humans. Roos J, Luz JM, Centoducati S, Sternglanz R, Lennarz WJ; Gene 1997;185:137-146. PMID:9034325

3: Enp1, a yeast protein associated with U3 and U14 snoRNAs, is required for pre-rRNA processing and 40S subunit synthesis. Chen W, Bucaria J, Band DA, Sutton A, Sternglanz R; Nucleic Acids Res 2003;31:690-699. PMID:12527778