title: Differential reactivities of lysines in calmodulin complexed to phosphatase.
abstract: Calmodulin and calmodulin complexed with calcineurin phosphatase were trace labeled with [3H]acetic anhydride and the incorporation of [3H]acetate into each epsilon-amino lysine of calmodulin was measured. The relative reactivities of calmodulin lysines were higher in the presence of Ca2+ than in the presence of EGTA, and the order was: Lys-75 greater than Lys-94 greater than Lys-148 greater than or equal to Lys-77 greater than Lys-13 greater than or equal to Lys-21 greater than Lys-30. The changes in relative reactivity implied a change in conformation. When calmodulin was complexed with the phosphatase, Lys-21, Lys-77, and Lys-148 were most protected, implying that these residues are at or near the interaction sites or are conformationally perturbed by the interaction. Lys-30 and Lys-75 were slightly protected, lysine 13 showed no change, while lysine 94 significantly increased in reactivity. Comparison with results obtained from myosin light chain kinase using a similar technique (Jackson, A. E., Carraway, K. L., III, Puett, D., and Brew, K. (1986) J. Biol. Chem. 261, 12226-12232) reveals that calmodulin may interact with each of the two enzymes similarly at or near Lys-21, Lys-75, and Lys-148; one difference with phosphatase is that complex formation also involved Lys-77. These findings suggest that calmodulin interacts differently with its target enzymes.
authors.affiliation: Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
authors.forename: M A
authors.initials: MA
authors.lastname: Winkler
authors.forename: V A
authors.initials: VA
authors.lastname: Fried
authors.forename: D L
authors.initials: DL
authors.lastname: Merat
authors.forename: W Y
authors.initials: WY
authors.lastname: Cheung
mesh_terms: D000085:Acetates / Q000378:metabolism; D019342:Acetic Acid; D000089:Acetic Anhydrides / Q000378:metabolism; D000818:Animals; D019703:Calcineurin; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002417:Cattle; D008239:Lysine / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*
chemical_list: D000085:Acetates; D000089:Acetic Anhydrides; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; C031800:acetic anhydride; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases; D008239:Lysine; D019342:Acetic Acid; D002118:Calcium