The invention provides retroviral envelope glycoproteins in which the cytoplasmic C-terminal tail (CTT) from N-terminus to C-terminus comprises or consists of a T-domain and an R-domain, wherein the R-domain is truncated from its C-terminus, and hybrid glycoproteins and retroviral, especially alpharetroviral, lentiviral or gammaretroviral vector particles containing the glycoprotein. The glycoproteins target the SLC1A5 receptor for target cell entry.