Analysis of suborganellar fractions from spinach and pea chloroplasts for calmodulin-binding proteins.
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.
D002148:Calmodulin-Binding Proteins; D002736:Chloroplasts / Q000648:ultrastructure*; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D010749:Phosphoprotein Phosphatases / Q000032:analysis*; D014675:Vegetables
D002148:Calmodulin-Binding Proteins; D010749:Phosphoprotein Phosphatases