Our research studies the interaction of the FeLV Env A5, previously identified through a RBD library screen, with its host receptor SLC35F2. The natural substrate for SLC35F2 has been identified to be the micronutrients queuine (q) and Queuosine, involved in modifying the tRNA of Asp, Tyr, Asn, and His at the wobble position. Our expanded studies verify and define the role of q/Q in the entry of the FeLV Env A5through competition studies of the drug YM155 with q/Q on SLC35F2 functions.

Using structural predictive methods, we have developed models of the SLC35F2 proteins with two conformations: open inwards towards the cytoplasmic face (EVSF->GGGG) and open outwards towards the extracellular space (AYL->GGG), if expressed on the cell surface. Based on these models, mutant SLC35F2 proteins were expressed in mammalian cells that are biased to each of these conformations. Differential functions have been identified for these two conformations, including the requirement for the virus to enter cells only when the SLC35F2 is open towards the extracellular space (AYL->GGG). Additional studies include subcellular localization to the mitochondria, transport of the drug YM155 and interactions with p53. Metabolomic studies on isolated mitochondria indicate that the principal component analysis of the WT SLC35F2 correlates with the mutant conformation bearing the EVSF-> GGGG changes.

Three Args within the 11 aa randomized RBD region were found to be essential for viral entry. Mutagenesis of the SLC35F2 surface exposed loops has identified acidic residues required for entry of the A5 Env virus. As viruses usurp cellular functions, it was found that amino acids in one of these acidic regions on the cell surface is required for YM155 transport in addition to residues located within the central pore.