Kinetics of Proton Binding to the Sarcoplasmic Reticulum Ca-ATPase in the E1 State

Fibich, Andreas; Janko, Karl; Apell, Hans-Jürgen

Kinetics of Proton Binding to the Sarcoplasmic Reticulum Ca-ATPase in the E1 State

Dateien

BJ_93_3092.pdf(365.38 KB)

Datum

2007

Autor:innen

Fibich, Andreas

Janko, Karl

Apell, Hans-Jürgen

Publikationstyp

Zeitschriftenartikel

Erschienen in

Biophysical Journal ; 93 (2007), 9. - S. 3092-3104. - ISSN 0006-3495

Zusammenfassung

A new caged proton, 2-methoxy-5-nitrophenyl sulfate, was synthesized and used in time-resolved pH jump experiments to study proton binding in the sarcoplasmic reticulum Ca-ATPase. The major advantage of this compound is that it does not produce significant artifacts in experiments in which the fluorescent styryl dye 2BITC is used to monitor ion movements in the Ca pump. Two rate-limiting processes were resolved and their dependence on pH, Ca21 concentration, and temperature investigated. The faster process showed a relaxation time between 4 and 8 ms independent on pH and Ca21 concentration, and the time constant of the slower process varied between 31 ms (0 Ca21) and 100 ms (100 mMCa21). A consistent mechanism to explain the results was derived in agreement with previous studies and the generally accepted Post-Albers scheme of the pump cycle. This mechanism requires that under physiological conditions the ion-binding sites are always occupied and two protons and a Ca21 ion replace each other. In the absence of ATP at low pH a nonphysiological state can be induced in which up to four protons bind to the Ca pump in the E1 conformation. So far it could not be verified whether these additional protons bind to amino acid side chains or are coordinated as hydronium ions.

Fachgebiet (DDC)

570 Biowissenschaften, Biologie

Zitieren

ISO 690

FIBICH, Andreas, Karl JANKO, Hans-Jürgen APELL, 2007. Kinetics of Proton Binding to the Sarcoplasmic Reticulum Ca-ATPase in the E1 State. In: Biophysical Journal. 93(9), pp. 3092-3104. ISSN 0006-3495. Available under: doi: 10.1529/biophysj.107.110791

BibTex

@article{Fibich2007Kinet-7558,
  year={2007},
  doi={10.1529/biophysj.107.110791},
  title={Kinetics of Proton Binding to the Sarcoplasmic Reticulum Ca-ATPase in the E1 State},
  number={9},
  volume={93},
  issn={0006-3495},
  journal={Biophysical Journal},
  pages={3092--3104},
  author={Fibich, Andreas and Janko, Karl and Apell, Hans-Jürgen}
}

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