The zinc-finger protein ZPR1 is ubiquitous among eukaryotes. It is indeed known to be an essential protein in yeast. In quiescent cells, ZPR1 is localized to the cytoplasm. But in proliferating cells treated with EGF or with other mitogens, ZPR1 accumulates in the nucleolus. ZPR1 interacts with the cytoplasmic domain of the inactive EGF receptor (EGFR) and is thought to inhibit the basal protein tyrosine kinase activity of EGFR. This interaction is disrupted when cells are treated with EGF, though by themselves, inactive EGFRs are not sufficient to sequester ZPR1 to the cytoplasm. Upon stimulation by EGF, ZPR1 directly binds the eukaryotic translation elongation factor-1alpha (eEF-1alpha) to form ZPR1/eEF-1alpha complexes. These move into the nucleus, localising particularly at the nucleolus. Indeed, the interaction between ZPR1 and eEF-1alpha has been shown to be essential for normal cellular proliferation, and ZPR1 is thought to be involved in pre-ribosomal RNA expression. The ZPR1 domain consists of an elongation initiation factor 2-like zinc finger and a double-stranded beta helix with a helical hairpin insertion. ZPR1 binds preferentially to GDP-bound eEF1A but does not directly influence the kinetics of nucleotide exchange or GTP hydrolysis. The alignment for this family shows a domain of which there are two copies in ZPR1 proteins. This family also includes several hypothetical archaeal proteins (from both Crenarchaeota and Euryarchaeota), which only contain one copy of the aligned region. This similarity between ZPR1 and archaeal proteins was not previously noted.