Restriction factor required to restrict infectivity of lentiviruses, such as HIV-1: acts by inhibiting an early step of viral infection. Impairs the penetration of the viral particle into the cytoplasm (PubMed:26416733, PubMed:26416734). Enhances the incorporation of serine into phosphatidylserine and sphingolipids. May play a role in providing serine molecules for the formation of myelin glycosphingolipids in oligodendrocytes (By similarity).
