TY - JOUR
T1 - pH dependent inactivation of solubilized F1F0 ATP synthase by dicyclohexylcarbodiimide
T2 - pKa of detergent unmasked aspartyl-61 in Escherichia coli subunit c
AU - Valiyaveetil, Francis
AU - Hermolin, Joe
AU - Fillingame, Robert H.
N1 - Funding Information:
This work was supported by United States Public Health Research Grant GM23105.
PY - 2002/2/15
Y1 - 2002/2/15
N2 - The pH dependence of the reaction of dicyclohexylcarbodiimide with the essential aspartyl-61 residue in subunit c of Escherichia coli ATP synthase was compared in membranes and in a detergent dispersed preparation of the enzyme. The rate of reaction was estimated by measuring the inactivation of ATPase activity. The reaction with the detergent dispersed form of the enzyme proved to be pH sensitive with the essential aspartyl group titrating with a pKa = 8. However, when measured with E. coli membranes, the reaction proved to be pH insensitive. The results suggest that the reacting aspartyl-61 residues are shielded from the bulk aqueous solvent when in the membrane, but then become aqueous-accessible following detergent solubilization.
AB - The pH dependence of the reaction of dicyclohexylcarbodiimide with the essential aspartyl-61 residue in subunit c of Escherichia coli ATP synthase was compared in membranes and in a detergent dispersed preparation of the enzyme. The rate of reaction was estimated by measuring the inactivation of ATPase activity. The reaction with the detergent dispersed form of the enzyme proved to be pH sensitive with the essential aspartyl group titrating with a pKa = 8. However, when measured with E. coli membranes, the reaction proved to be pH insensitive. The results suggest that the reacting aspartyl-61 residues are shielded from the bulk aqueous solvent when in the membrane, but then become aqueous-accessible following detergent solubilization.
KW - ATP synthase
KW - ATPase inhibition
KW - Dicyclohexylcarbodiimide
KW - Essential carboxyl
KW - Proton transport
KW - Subunit c
KW - pH dependence
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U2 - 10.1016/S0005-2728(01)00251-1
DO - 10.1016/S0005-2728(01)00251-1
M3 - Article
C2 - 11997138
AN - SCOPUS:0037085021
SN - 0005-2728
VL - 1553
SP - 296
EP - 301
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 3
ER -