Abstract
Subcellular distribution of calmodulin within wheat leaf cells was measured by a enzymatic method (activation of calmodulin‐deficient NAD kinase from pea seedlings) or a radioimmunoassay. Most of cellular calmodulin was localized in cytosol fraction (89–93%), and remainders were in the mitochondrial (5–9%), the chloroplast (1–2%) and the microsomal (< 1%) fractions. Calmodulin concentration in the chloroplast was sufficient to saturate NAD kinase which was localized mostly in the chloroplast. Therefore, the light‐induced Ca2+ transport in intact wheat chloroplasts (Muto, S. FEBS Lett. (1982) 139, 250–254] may play an important role in regulation of chloroplast NAD kinase activity.