The elongation factor-1 complex is composed of two subunits, EF-1 α1 (elongation factor 1-alpha 1) and EF-1 α2 (elongation factor 1-alpha 2), and is responsible for the delivery of aminoacyl tRNAs to the ribosome. EF-1 α1 is expressed predominately in brain, placenta, lung, liver, kidney and pancreas, while EF-1 α2 is highly expressed in heart, brain and skeletal muscle. Both EF-1 α1 and α2 localize to the nucleus and belong to the GTP-binding elongation factor family. The gene encoding EF-1 α2, which maps to human chromosome 20q13.3, may play a role in the development of ovarian cancer, while the EF-1 α1 gene, mapping to chromosome 6Q14.1, is commonly present as an autoantigen in patients with Felty syndrome. Felty syndrome is a disorder characterized by rheumatoid arthritis, a swollen spleen, decreased white blood cell count, and increased susceptibility to infection.