Disease relevance of tentoxin

• Tentoxin is a naturally occurring phytotoxic peptide that causes seedling chlorosis and arrests growth in sensitive plants and algae [1].
• Combining this substitution with either additional replacements in the alpha-subunit (Q49A, L95A, E96Q, I273M) or the replacement of Ser(59) in the beta-subunit enhanced the sensitivity to the inhibitor and resulted in a complete inhibition of the E. coli F(1)-ATPase by the plant-specific inhibitor tentoxin [2].
• Hybrid Rhodospirillum rubrum F(0)F(1) ATP synthases containing spinach chloroplast F(1) beta or alpha and beta subunits reveal the essential role of the alpha subunit in ATP synthesis and tentoxin sensitivity [3].

High impact information on tentoxin

• Plastid atpB genes from six closely related, tentoxin-sensitive or -resistant Nicotiana species differ at codon 83, according to their response to the toxin: glutamate correlated with resistance and aspartate correlated with sensitivity [1].
• Tentoxin seems to act by inhibiting inter-subunit contacts at the alphabeta-interface and by blocking the interconversion of binding sites in the catalytic mechanism [4].
• Characteristics of the reconstituted ATPase were very close to those of the native complex, including methanol-reversible inhibition by the purified epsilon subunit of CF1 and sensitivity to inhibition by azide and by tentoxin [5].
• At low concentrations, tentoxin inhibits ATP hydrolysis of ensembles of F(1) molecules in solution [6].
• To clarify the role of the alpha subunit in the rebinding of beta, restoration of catalytic function, and conferral of sensitivity to the chloroplast-specific inhibitor tentoxin, LiCl-treated chromatophores were analyzed by immunoblotting before and after reconstitution with mixtures of R. rubrum and chloroplast alpha and beta subunits [3].

Biological context of tentoxin

• The alga, normally tentoxin-resistant, was rendered tentoxin-sensitive by mutagenesis of its plastid atpB gene at codon 83 [1].
• The analysis of the kinetics of tentoxin binding on the low affinity site of the enzyme showed strong evidence for an interaction between this site and the nucleotide binding sites and revealed a complex relationship between the catalytic state and the reactivation process [7].
• However, only the phosphorylation activity of the mutant betaE83D was inhibited by tentoxin with 50% inhibition attained at 4 microM [8].
• The hybrid system was further used to examine the effects of amino acid substitution at position 83 of the beta subunit on sensitivity to tentoxin [3].
• 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 [9].

Anatomical context of tentoxin

• In contrast, chromatophores reconstituted with the native R. rubrum beta subunit actively hydrolyzed both Mg2+-ATP and Ca2+-ATP and were insensitive to tentoxin [10].
• It showed the same efficiency as tentoxin in inhibition of ATPase activity of the isolated chloroplast F1 proton ATPase (CF1) as well as in inhibition of the ATP synthase activity of the membrane-bound enzyme (CF0CF1) in thylakoids and proteoliposomes [11].
• Tentoxin interacted with rat liver microsomes and the difference spectrum was characteristic of binding to a protein site close to the heme [12].
• Potassium transport through lipid bilayer membranes facilitated by tentoxin dimers. A new mechanism of ion carrier transport [13]?
• Effects of tentoxin and dihydrotentoxin on human erythrocytes [14].

Associations of tentoxin with other chemical compounds

• 2. DCCD modification of soluble CF1 eliminates one adenine nucleotide binding site which is exposed by dithiothreitol activation or by incubation with tentoxin [15].
• The transit peptide gene of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase from Nicotiana plumbaginifolia was fused to the tentoxin-resistant beta-subunit gene of chloroplast coupling factor 1 (CF1) from Nicotiana tabacum via a linker sequence [16].
• The anomalous effect of FCCP on the rate of ATP synthesis disappeared when the ATPase was partially blocked by the reversible inhibitor venturicidin, but not in the presence of tentoxin, an irreversible inhibitor [17].
• This increase was strongly inhibited by a treatment of the chloroplasts with the CF0 ATP synthase inhibitor DCCD, but unaffected by the CF1 ATPase inhibitor, tentoxin [18].
• At the end of this process dihydrotentoxin, the direct precursor of tentoxin, is released from the synthetase probably by cyclization [19].

Gene context of tentoxin

• Catalytic properties and sensitivity to tentoxin of Chlamydomonas reinhardtii ATP synthases changed in codon 83 of atpB by site-directed mutagenesis [8].
• 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 [9].
• The mechanism of action of tentoxin on the soluble part (chloroplast F1 H+-ATPase; CF1) of chloroplast ATP synthase was analyzed in the light of new kinetic and equilibrium experiments [7].
• However, its pretreatment with high tentoxin concentrations resulted in a remarkable 50-fold stimulation of the MgATPase activity as well as stabilization of its hexameric structure, thus enabling the isolation of a more active CF1-alpha 3 beta 3 complex by size-exclusion chromatography [20].
• Tentoxin exhibited a high affinity for P-450 3A (Ks approximately 10 microM) [12].

Analytical, diagnostic and therapeutic context of tentoxin

• Tentoxin binding on chloroplast coupling factor 1 (CF1) was studied using a centrifugation column method followed by HPLC analysis [21].

References