Temperature-induced states of isolated F1-ATPase affect catalysis, enzyme conformation and high-affinity nucleotide binding sites.
Isolated, nucleotide-depleted bovine-heart F1-ATPase exhibits a break in Arrhenius plot with a 2.7-fold increase in activation energy of ATP hydrolysis below 18-19 degrees C. Analysis of intrinsic tyrosine fluorescence and of the circular dichroism of F1-ATPase showed an abrupt and reversible conformational change occurring at the break temperature, characteristic of a structural tightening at low temperature. Analysis of catalytic nucleotide binding sites using fluorescent ADP analog, 3'-O-(1-naphthoyl)adenosine diphosphate did not show any significant change in affinity of nucleotide binding around the transition temperature but the bound fluorophore exerted a more restricted motion and slower rotation at temperature below the break, indicating a change in the mobility of groups in the close neighbourhood. It is concluded that, as a result of temperature, two kinetically distinct states of F1-ATPase are induced, due to a change in enzyme conformation, which influences directly the properties of catalytic nucleotide binding sites.
Baracca
A
A
Department of Biology, University of Bologna, Italy.
Amler
E
E
Solaini
G
G
Parenti Castelli
G
G
Lenaz
G
G
Houstek
J
J
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D002417:Cattle; D002942:Circular Dichroism; D005453:Fluorescence; D008929:Mitochondria, Heart / Q000201:enzymology*; D009711:Nucleotides / Q000378:metabolism*; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics
D009711:Nucleotides; D000244:Adenosine Diphosphate; C032458:3'-O-(naphthoyl-1)adenosine diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases