89 research outputs found
Link between allosteric signal transduction and functional dynamics in a multi-subunit enzyme: S-adenosylhomocysteine hydrolase
S-adenosylhomocysteine hydrolase (SAHH), a cellular enzyme that plays a key
role in methylation reactions including those required for maturation of viral
mRNA, is an important drug target in the discovery of antiviral agents. While
targeting the active site is a straightforward strategy of enzyme inhibition,
evidences of allosteric modulation of active site in many enzymes underscore
the molecular origin of signal transduction. Information of co-evolving
sequences in SAHH family and the key residues for functional dynamics that can
be identified using native topology of the enzyme provide glimpses into how the
allosteric signaling network, dispersed over the molecular structure,
coordinates intra- and inter-subunit conformational dynamics. To study the link
between the allosteric communication and functional dynamics of SAHHs, we
performed Brownian dynamics simulations by building a coarse-grained model
based on the holo and ligand-bound structures. The simulations of
ligand-induced transition revealed that the signal of intra-subunit closure
dynamics is transmitted to form inter-subunit contacts, which in turn invoke a
precise alignment of active site, followed by the dimer-dimer rotation that
compacts the whole tetrameric structure. Further analyses of SAHH dynamics
associated with ligand binding provided evidence of both induced fit and
population shift mechanisms, and also showed that the transition state ensemble
is akin to the ligand-bound state. Besides the formation of enzyme-ligand
contacts at the active site, the allosteric couplings from the residues distal
to the active site is vital to the enzymatic function.Comment: 35 pages, 14 figures, 3 Table
A New and Versatile Synthesis of 1,3-Dioxan-5-yl-pyrimidine and Purine Nucleoside Analogues
1,3-Dioxan-5-yl pyrimidine and purine nucleoside analogues
were prepared following a new and versatile synthetic strategy. These
analogues were synthesized via nucleophilic addition of the selected
nucleobase to a 1,3-dioxane scaffold that presents an appropriate leaving
group in position 5. In particular cis and trans isomers of purine/pyrimidine
nucleosides and their halogenated homologues were obtained.
NMR experiments, carried out on the cis isomers, led to
assignment of an equatorial orientation to the 2-hydroxymethyl group
and axial orientation to the nucleobase in position 5 of the 1,3-dioxane.
The trans isomers showed a diequatorial orientation of these groups.
These assignments were confirmed by X-ray crystallographic studie
Dual Actions of A2A and A3 Adenosine Receptor Ligand Prevents Obstruction-Induced Kidney Fibrosis in Mice
Kidney fibrosis is the final outcome of chronic kidney disease (CKD). Adenosine plays a significant role in protection against cellular damage by activating four subtypes of adenosine receptors (ARs), A1AR, A2AAR, A2BAR, and A3AR. A2AAR agonists protect against inflammation, and A3AR antagonists effectively inhibit the formation of fibrosis. Here, we showed for the first time that LJ-4459, a newly synthesized dual-acting ligand that is an A2AAR agonist and an A3AR antagonist, prevents the progression of tubulointerstitial fibrosis. Unilateral ureteral obstruction (UUO) surgery was performed on 6-week-old male C57BL/6 mice. LJ-4459 (1 and 10 mg/kg) was orally administered for 7 days, started at 1 day before UUO surgery. Pretreatment with LJ-4459 improved kidney morphology and prevented the progression of tubular injury as shown by decreases in urinary kidney injury molecular-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) excretion. Obstruction-induced tubulointerstitial fibrosis was attenuated by LJ-4459, as shown by a decrease in fibrotic protein expression in the kidney. LJ-4459 also inhibited inflammation and oxidative stress in the obstructed kidney, with reduced macrophage infiltration, reduced levels of pro-inflammatory cytokines, as well as reduced levels of reactive oxygen species (ROS). These data demonstrate that LJ-4459 has potential as a therapeutic agent against the progression of tubulointerstitial fibrosis
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