QR1, named from the cDNA, QR1, cloned from the neuroretina of quail,
Coturni. coturnix has 676 residues. Its C-terminal portion is similar
to the extracellular glycoprotein, BM40. QR1 and BM40 are the only
examples of (normally) extracellular EF-hands proteins. "Transcription
of QR1 takes place only during the late phase of retinal development
and is shut off sharply at hatching." .