LepA (GUF1 in Saccaromyces), now called elongation factor 4, is a GTP-binding membrane protein related to EF-G and EF-Tu. Two types of phylogenetic tree, rooted by other GTP-binding proteins, suggest that eukaryotic homologs (including GUF1 of yeast) originated within the bacterial LepA family. The function is unknown. [Unknown function, General]