SPX domain of the xenotropic and polytropic retrovirus receptor 1 (XPR1) and related proteins.
This region has been named the SPX domain after (Syg1, Pho81 and XPR1). The domain is found at the amino terminus of a variety of proteins. The N-terminus of the human XPR1 protein (xenotropic and polytropic retrovirus receptor 1) binds directly to the beta subunit of the G-protein heterotrimer leading to increased production of cAMP. These findings suggest that all members of this family are involved in G-protein associated signal transduction. Several members of this family are annotated as XPR1 proteins: the xenotropic and polytropic retrovirus receptor confers susceptibility to infection with xenotropic and polytropic murine leukaemia viruses (MLV). Infection by these retroviruses can inhibit XPR1-mediated cAMP signaling and result in cell toxicity and death. Similarity between Syg1, phosphate regulators and XPR1 sequences has been previously noted, as has the additional similarity to several predicted proteins, of unknown function, from Drosophila melanogaster, Arabidopsis thaliana, Caenorhabditis elegans, Schizosaccharomyces pombe, and Saccharomyces cerevisiae, and many other diverse organisms.
Jiyao W et al.(2023). "The conserved domain database in 2023.",