The calmodulin-binding domain mediates the self-association of the plasma membrane Ca2+ pump

• Published in: The Journal of biological chemistry Vol. 266; no. 1; pp. 22 - 27
• Main Authors: Vorherr, T, Kessler, T, Hofmann, F, Carafoli, E
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 05.01.1991; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Antibodies - isolation & purification; Antigen-Antibody Complex; Binding Sites; Biological and medical sciences; Calcium-Transporting ATPases - blood; Calmodulin - metabolism; Cattle; Cell physiology; Erythrocyte Membrane - enzymology; Fundamental and applied biological sciences. Psychology; Humans; Kinetics; Macromolecular Substances; Membrane and intracellular transports; Molecular and cellular biology; Molecular Sequence Data; Peptides - chemical synthesis; Spectrometry, Fluorescence; Human; Oligomerization; Membrane pump; Calcium; ATPase; Binding site; Calmodulin; Fluorescence spectrometry; Immunological method
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)52395-4

Dimerization (oligomerization) of the plasma membrane Ca2+ pump increases its activity (Kosk-Kosicka, D., Bzdega, T., and Wawrzynow, A. (1989) J. Biol. Chem. 264, 19495-19499). Fluorescence titration on preparations of the purified eosin-labeled human erythrocyte ATPase has been used to monitor the oligomerization process. Calmodulin inhibits oligomerization, although it can bind to the oligomerized enzyme. Synthetic peptides corresponding to the calmodulin-binding domain of the pump stimulate its ATPase activity, indicating the formation of heterooligomers of the peptides with the pump. The oligomerization is prevented by the preincubation of the ATPase with calmodulin. Polyclonal antibodies against the synthetic calmodulin-binding domain inhibit its basal and its calmodulin-stimulated ATPase activity and prevent the formation of the oligomers. ATPase preparations truncated at the COOH terminus with calpain to a fragment of 124 kDa which does not contain the calmodulin-binding domain fail to oligomerize with the intact ATPase. The results show that the calmodulin-binding domain mediates the oligomerization of the Ca2+ pump.