Inactivation of the wild-type human plasma membrane Ca2+ pump (isoform 4b) by fluorescein isothiocyanate is accompanied by covalent modification of Lys591. The mutation of Lys591 to arginine reduced the Ca2+ transport activity to 35% of the wild-type, and diminished the amount of acylphosphate formed from ATP by a corresponding amount. When this mutant was treated with fluorescein isothiocyanate, the enzyme was still irreversibly inactivated, even though no reactive residue was available at position 591. The results show that, although Ca2+ pump function is sensitive to the residue at position 591, Lys591 is not essential for enzyme activity. They also demonstrate that irreversible inhibition of the plasma membrane Ca2+ pump by fluorescein isothiocyanate does not require the covalent modification of Lys591. This indicates that fluorescein isothiocyanate reacts with lysine residues at other positions in addition to Lys591.
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July 1996
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Research Article|
July 01 1996
The plasma membrane Ca2+ pump mutant lysine591 → arginine retains some activity, but is still inactivated by fluorescein isothiocyanate
Hugo P. ADAMO;
Hugo P. ADAMO
*Instituto de Quimica y Fisicoquimica Biologica (UBA-CONICET), Facultad de Farmacia y Bioquimica, Buenos Aires, Argentina
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Adelaida G. FILOTEO;
Adelaida G. FILOTEO
†Department of Biochemistry and Molecular Biology, Mayo Clinic/Foundation, Rochester, MN 55905, U.S.A.
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John T. PENNISTON
John T. PENNISTON
‡
†Department of Biochemistry and Molecular Biology, Mayo Clinic/Foundation, Rochester, MN 55905, U.S.A.
‡To whom correspondence should be addressed: Guggenheim 1642D, Mayo Clinic, 200 First Street South West, Rochester, MN 55905, U.S.A.
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Publisher: Portland Press Ltd
Received:
January 12 1996
Revision Received:
February 28 1996
Accepted:
February 29 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 317 (1): 41–44.
Article history
Received:
January 12 1996
Revision Received:
February 28 1996
Accepted:
February 29 1996
Citation
Hugo P. ADAMO, Adelaida G. FILOTEO, John T. PENNISTON; The plasma membrane Ca2+ pump mutant lysine591 → arginine retains some activity, but is still inactivated by fluorescein isothiocyanate. Biochem J 1 July 1996; 317 (1): 41–44. doi: https://doi.org/10.1042/bj3170041
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