Synthesis and stability of phosphate modified ATP analogues
Although ATP activates all P2X receptor subunits, αβmeATP is effective only at those containing a P2X1 or P2X3 subunit. This discrimination on the basis of a single –O– to –CH2– substitution suggested that it may be possible to develop ATP analogues with modified phosphate chains that might be useful to separate activity at the P2X2 and P2X2/3 subunits. In the present study, we have synthesised several such analogues and compared their activity as agonists and antagonists at heterologously expressed homomeric P2X2 and heteromeric P2X2/3 receptors.
Synthesis of c-phosphate modified ATP analogues 1–10
N2 - Aliphatic amino acid analogues of L methionine that inhibit the enzymatic synthesis of S adenosyl L methionine were designed on the basis of structural, conformational, and electronic considerations. The inhibitory activity of these compounds was evaluated with partially purified preparations of ATP:L methionine S adenosyltransferase (EC 220.127.116.11) obtained from bakers' yeast, E. coli, and rat liver. The effects of variation in length and branching of carbon chain, steric configuration, degree or position of unsaturation, and the introduction of chloro groups were analyzed in an effort to deduce the most favorable features for inhibition. Within this class of compounds, 2 amino 4 hexynoic acid, (E) 2 amino trans 4 hexenoic acid, and (Z) 2 amino 5 chloro trans 4 hexenoic acid are among the most powerful inhibitors synthesized. In contrast, (Z) 2 amino cis 4 hexenoic acid and (E) 2 amino 5 chloro cis 4 hexenoic acid are weak inhibitors or are inactive. The activity of the more powerful inhibitors appears to reside exclusively in the L isomers. (Z) L 2 Amino 5 chloro trans 4 hexenoic acid displays considerably greater specificity for the inhibition of rat liver enzyme (I50 = 0.55 mM) than for the yeast (I50 = 3.0 mM) or E. coli (I50 = 4.2 mM) adenosyltransferase. Examination of molecular models reveals a close similarity in the size, shape, and molecular contour between an extended conformation of L methionine and L 2 amino 4 hexynoic acid and (Z) L 2 amino 5 chloro trans 4 hexenoic acid. Another compound with significant inhibitory activity is (2S, 4S) 2 amino 4,5 methylene 5 hexenoic acid (hypoglycin A).
Grandolini G, Luana P and Ambrogi V. Synthesis of some new 1,4-benzothiazine and 1,5-benzothiazepine tricyclic derivatives with structural analogy with TIBO and their screening for anti-HIV activity. Eur J Med Chem 1999; 34:701-709.
A novel route of ATP synthesis - [PDF Document]
We report the inhibition of mammalian polyadenylation by the triphosphate derivatives of adenosine analogues, 8-chloroadenosine (8-Cl-Ado) and 8-aminoadenosine (8-amino-Ado), which are under preclinical and clinical investigations for the treatment of hematological malignancies. The nucleotide substrate specificity of bovine poly(A) polymerase (PAP) towards C8-modified ATP analogues was examined using primer extension assays. Radiolabeled RNA primers were incubated with bovine PAP, and in the absence of ATP, no primer extension was observed with 8-Cl-ATP, whereas 8-amino-ATP resulted in chain termination. The effects of modified ATP analogues on ATP-dependent poly(A)-tail synthesis by bovine PAP also were determined, and incubation with analogue triphosphate resulted in significant reduction of poly(A)-tail length. To model the biochemical consequences of 8-Cl-Ado incorporation into RNA, a synthetic RNA primer containing a 3′-terminal 8-Cl-AMP residue was evaluated, and polyadenylation of the primer by bovine PAP with ATP was blocked completely. To explain these experimental observations and probe the possible structural mechanisms, molecular modeling was employed to examine the interactions between PAP and various ATP analogues. Molecular docking demonstrated that C8-modifications of ATP led to increased distance between the 3′-hydroxyl group of the RNA oligonucleotide terminus and the α-phosphate of ATP that render the molecules in an unfavorable position for incorporation into RNA. Similarly, C8-substitution with a chlorine or amino group at the 3′-terminal residue of RNA also inhibits further chain elongation by PAP. In conclusion, modified ATP analogues may exert their biological effects through polyadenylation inhibition, and thus may provide an RNA-directed mechanism of action for 8-Cl-Ado and 8-amino-Ado.
Interaction of Atp Analogues with Myosin - Ralph Yount
AB - Recent studies have shown that novobiocin (NB), a member of the coumermycin (CA) family of antibiotics with demonstrated DNA gyrase inhibitory activity, inhibits Heat shock protein 90 (HSP90) by binding weakly to a putative ATP-binding site within its C-terminus. To develop more potent HSP90 inhibitors that target this site and to define structure-activity relationships (SARs) for this class of compounds, we have synthesized twenty seven 3-amido-7- noviosylcoumarin analogues starting from NB and CA. These were evaluated for evidence of HSP90 inhibition using several biological assays including inhibition of cell proliferation and cell cycle arrest, induction of the heat shock response, inhibition of luciferase-refolding in vitro, and depletion of the HSP90 client protein c-erbB-2/HER-2/neu (HER2). This SAR study revealed that a substantial increase in biological activity can be achieved by introduction of an indole-2-carboxamide group in place of 4-hydroxy-isopentylbenzamido group at C-3 of NB in addition to removal/derivatization of the 4-hydroxyl group from the coumarin ring. Methylation of the 4-hydroxyl group in the coumarin moiety moderately increased biological activity as shown by compounds 11 and 13. Our most potent new analogue 19 demonstrated biological activities consistent with known HSP90-binding agents, but with greater potency than NB.