TY - JOUR
T1 - Differentiation of the nucleotide-binding sites on nucleotide-depleted mitochondrial F1-ATPase by means of a fluorescent ADP analogue
AU - Weber, Joachim
AU - Schmitt, Sabine
AU - Grell, Ernst
AU - Schäfer, Günter
PY - 1990/7/5
Y1 - 1990/7/5
N2 - The interaction of the fluorescent ADP analogue linbenzo-ADP (containing a linearly extended version of adenine, in which a benzene ring is inserted between pyrimidine and imidazole ring) with nucleotide-depleted mitochondrial F1 was investigated. It was found that lin-benzo-ADP is able to occupy all six nucleotide-binding sites present on the enzyme. Two sites exhibit a very high affinity for the analogue (dissociation constant, Kd, < 10 nM) and bind it rapidly (association rate constant, k+1, about 1·106 M-1 s-1). A third site shows a lower affinity for the analogue (Kd = 1-2 μM) and is occupied relatively fast (k+1 ≈ 104 M-1 s-1). Binding of lin-benzo-ADP to these three sites is prevented not only in the presence of excess ADP and ATP, but also by IDP and ITP, thus indicating that these sites are the catalytic ones. As it will be discussed, this conclusion is further corroborated by the finding that release of the analogue from the two high affinity sites can be promoted by binding of nucleoside di- and triphosphates to the third site. The remaining three sites were found to bind lin-benzo-ADP with identical affinity (Kd =1-2 μM) and with a rather low association rate (k+1 = 300-600 M-1 s-1). Binding of the analogue to them is only prevented by ADP and ATP, but not by IDP and ITP, which confirms that these sites are the noncatalytic ones. The analogue could be displaced by excess ADP also from these sites; however, in contrast to the catalytic sites, no promotive effect was observed here. The obvious changes in the nucleotide binding behavior of the non-catalytic sites after depletion of endogenous nucleotides will be discussed.
AB - The interaction of the fluorescent ADP analogue linbenzo-ADP (containing a linearly extended version of adenine, in which a benzene ring is inserted between pyrimidine and imidazole ring) with nucleotide-depleted mitochondrial F1 was investigated. It was found that lin-benzo-ADP is able to occupy all six nucleotide-binding sites present on the enzyme. Two sites exhibit a very high affinity for the analogue (dissociation constant, Kd, < 10 nM) and bind it rapidly (association rate constant, k+1, about 1·106 M-1 s-1). A third site shows a lower affinity for the analogue (Kd = 1-2 μM) and is occupied relatively fast (k+1 ≈ 104 M-1 s-1). Binding of lin-benzo-ADP to these three sites is prevented not only in the presence of excess ADP and ATP, but also by IDP and ITP, thus indicating that these sites are the catalytic ones. As it will be discussed, this conclusion is further corroborated by the finding that release of the analogue from the two high affinity sites can be promoted by binding of nucleoside di- and triphosphates to the third site. The remaining three sites were found to bind lin-benzo-ADP with identical affinity (Kd =1-2 μM) and with a rather low association rate (k+1 = 300-600 M-1 s-1). Binding of the analogue to them is only prevented by ADP and ATP, but not by IDP and ITP, which confirms that these sites are the noncatalytic ones. The analogue could be displaced by excess ADP also from these sites; however, in contrast to the catalytic sites, no promotive effect was observed here. The obvious changes in the nucleotide binding behavior of the non-catalytic sites after depletion of endogenous nucleotides will be discussed.
UR - http://www.scopus.com/inward/record.url?scp=0025369304&partnerID=8YFLogxK
M3 - Article
C2 - 2141603
AN - SCOPUS:0025369304
SN - 0021-9258
VL - 265
SP - 10884
EP - 10892
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 19
ER -