Purified chloroplasts from spinach and pea leaves were subfractionated into envelope, thylakoid, and stroma fractions and were analyzed for calmodulin-binding proteins using a 125I-calmodulin gel overlay assay. Calmodulin binding was primarily associated with a major polypeptide (Mr 33,000) in the envelope membrane fraction. In contrast, major calmodulin-binding proteins were not detected in the thylakoid or stroma fractions. Our results provide the first evidence of calmodulin-binding proteins in the chloroplast envelope, and raise the possibility that calmodulin may contribute to the regulation of chloroplast function through its interaction with calmodulin-binding proteins in the chloroplast envelope. In addition, our results combined with those of other investigators support the proposal that subcellular organelles may be a primary site of calmodulin action.
Analysis of suborganellar fractions from spinach and pea chloroplasts for calmodulin-binding proteins.
D M Roberts, R E Zielinski, M Schleicher, D M Watterson; Analysis of suborganellar fractions from spinach and pea chloroplasts for calmodulin-binding proteins.. J Cell Biol 1 November 1983; 97 (5): 1644–1647. doi: https://doi.org/10.1083/jcb.97.5.1644
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