Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The effect of energy transfer inhibitors on energy-dependent exchange of tightly bound adenine nucleotides with washed, broken spinach thylakoids has been studied. Energy transfer inhibitors that inhibit the ATPase activity of soluble chloroplast coupling factor 1 (CF1) (e.g. phloridzin and tentoxin) do not inhibit energy-dependent adenine nucleotide exchange. Energy transfer inhibitors that block proton flux through the hydrophobic protein proton channel (CF0) (e.g. dicyclohexylcarbodiimide and triphenyltin chloride) also block light-dependent adenine nucleotide exchange. 2. Tentoxin, at relatively high concentrations, stimulates an energy-independent exchange of adenosine diphosphate. 3. High concentrations of tentoxin elicit a Ca2+-dependent ATPase activity with soluble CF1, but has no effect on the Ca2+-dependent ATPase activity of membrane-bound CF1. 4. The trypsin-activated, Ca2+-dependent, membrane-bound ATPase is not affected by high concentrations of tentoxin, whereas the dithiothreitol-activated, Mg2+-dependent ATPase is markedly inhibited. 5. The reconstitution of chloroplasts, partially depleted in CF1, with soluble CF1 is correlated with the loss of tentoxin-induced, Ca2+-dependent ATPase activity associated with soluble CF1.
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PMID:Tentoxin-induced energy-independent adenine nucleotide exchange and ATPase activity with chloroplast coupling factor 1. 15 81

Tentoxin, a cyclic tetrapeptide produced by the fungus Alternaria tenuis, is a potent inhibitor of the chloroplast coupling factor 1 from certain sensitive species of plants. We have shown that the beta subunit is at least partly responsible for conferring sensitivity to the toxin. This was confirmed by Avni et al. (Avni, A., Anderson, J.D., Holland, N., Rochaix, J-D., Gromet-Elhanan, Z., and Edelman, M. (1992) Science 257, 1245-1247) who demonstrated the importance for tentoxin sensitivity of an acidic amino acid residue at position 83 in the beta subunit sequence. In this paper we show that the Ca(2+)-ATPase and Mg(2+)-ATPase activities of CF1 lacking the delta and epsilon subunits, CF1(-delta epsilon), were fully sensitive to tentoxin, even after the gamma subunit is cleaved by trypsin into several smaller fragments. We also show that the isolated reconstitutively active beta subunit of CF1 does not effectively compete with CF1(-delta epsilon) for tentoxin binding. The results suggest that tight tentoxin binding requires the presence of at least the alpha and beta subunits but is independent of the delta and epsilon subunits. Tentoxin inhibited the release of a tightly bound molecule of ADP from CF1, which was induced by the binding of the ATP analogue adenylyl-beta,gamma-imidodiphosphate (AMP-PNP). AMP-PNP was shown previously (Shapiro, A.B., and McCarty, R.E. (1990) J. Biol. Chem. 265, 4340-4347) to cause two adenine nucleotide binding sites on CF1, sites 1 and 3, to switch their properties, possibly as part of an alternating site catalytic cooperativity mechanism (Boyer, P.D. (1989) FASEB J. 3, 2164-2178). It is proposed that the effect of tentoxin on catalytic cooperativity in CF1 results from tentoxin binding at an interface between alpha and beta subunits, preventing transfer of information between different nucleotide binding sites on the enzyme.
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PMID:Inhibition by tentoxin of cooperativity among nucleotide binding sites on chloroplast coupling factor 1. 847 98