Membrane crystals of Ca2+-ATPase in sarcoplasmic reticulum of developing muscle

The vanadate-induced crystallization of Ca2+-ATPase was analyzed on sarcoplasmic reticulum vesicles isolated between 10 and 28 days of development from pectoralis muscles of chicken. After exposure to Na3VO4 in a Ca2+-free medium, Ca2+-ATPase crystals begin to appear on portions of the surface of a few vesicles, isolated at 18 days of development. Thereafter, the number of vesicles containing Ca2+-ATPase crystals rapidly increases and after 1 week of postnatal development (28 days), it reaches the adult level of about 30% of the vesicle population. These observations are discussed with reference to the mechanism of Ca2+-ATPase crystallization and the regulation of sarcoplasmic reticulum biosynthesis.