- Phosphorylation compromises FAD binding and intracellular stability of wild-type and cancer-associated NQO1: Insights into flavo-proteome stability. [Journal Article]
- IJInt J Biol Macromol 2018 Sep 19
- Over a quarter million of protein phosphorylation sites have been identified so far, although the effects of site-specific phosphorylation on protein function and stability, as well as their possible...
Over a quarter million of protein phosphorylation sites have been identified so far, although the effects of site-specific phosphorylation on protein function and stability, as well as their possible impact in the phenotypic manifestation in genetic diseases are vastly unknown. We investigated here the effects of phosphorylating S82 in human NADP(H):quinone oxidoreductase 1, a representative example of disease-associated flavoprotein in which protein stability is coupled to the intracellular flavin levels. Additionally, the cancer-associated P187S polymorphism causes inactivation and destabilization of the enzyme. By using extensive in vitro and in silico characterization of phosphomimetic S82D mutations, we showed that S82D locally affected the flavin binding site of the wild-type (WT) and P187S proteins thus altering flavin binding affinity, conformational stability and aggregation propensity. Consequently, the phosphomimetic S82D may destabilize the WT protein intracellularly by promoting the formation of the degradation-prone apo-protein. Noteworthy, WT and P187S proteins respond differently to the phosphomimetic mutation in terms of intracellular stability, further supporting differences in molecular recognition of these two variants by the proteasomal degradation pathway. We propose that phosphorylation could have critical consequences on stability and function of human flavoproteins, important for our understanding of genotype-phenotype relationships in their related genetic diseases.
- Severe riboflavin deficiency induces alterations in the hepatic proteome of starter Pekin ducks. [Journal Article]
- BJBr J Nutr 2017; 118(9):641-650
- Suboptimal vitamin B2 status is encountered globally. Riboflavin deficiency depresses growth and results in a fatty liver. The underlying mechanisms remain to be established and an overview of molecu...
Suboptimal vitamin B2 status is encountered globally. Riboflavin deficiency depresses growth and results in a fatty liver. The underlying mechanisms remain to be established and an overview of molecular alterations is lacking. We investigated hepatic proteome changes induced by riboflavin deficiency to explain its effects on growth and hepatic lipid metabolism. In all, 360 1-d-old Pekin ducks were divided into three groups of 120 birds each, with twelve replicates and ten birds per replicate. For 21 d, the ducks were fed ad libitum a control diet (CAL), a riboflavin-deficient diet (RD) or were pair-fed with the control diet to the mean daily intake of the RD group (CPF). When comparing RD with CAL and CPF, growth depression, liver enlargement, liver lipid accumulation and enhanced liver SFA (C6 : 0, C12 : 0, C16 : 0, C18 : 0) were observed. In RD, thirty-two proteins were enhanced and thirty-one diminished (>1·5-fold) compared with CAL and CPF. Selected proteins were confirmed by Western blotting. The diminished proteins are mainly involved in fatty acid β-oxidation and the mitochondrial electron transport chain (ETC), whereas the enhanced proteins are mainly involved in TAG and cholesterol biosynthesis. RD causes liver lipid accumulation and growth depression probably by impairing fatty acid β-oxidation and ETC. These findings contribute to our understanding of the mechanisms of liver lipid metabolic disorders due to RD.
- Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). [Guideline]
- AAutophagy 2016; 12(1):1-222
- Comparative evaluation of accuracy of periodontal probing depth and attachment levels using a Florida probe versus traditional probes. [Journal Article]
- MJMed J Armed Forces India 2015; 71(4):352-8
- CONCLUSIONS: Florida probe and CEJ probe have been shown to be more accurate and were found to be more consistent which were reproducible by two independent examiners.
- Comparative evaluation of surgical modalities for coverage of gingival recession: An Armed Forces Medical College perspective. [Journal Article]
- MJMed J Armed Forces India 2015; 71(1):53-9
- CONCLUSIONS: Connective tissue grafts were statistically significantly superior to guided tissue regeneration for improvement in gingival recession reduction.
- [Effect of periodontal therapy on metabolic control and serum biochemical markers in subjects with type 2 diabetes and chronic periodontitis]. [Journal Article]
- BDBeijing Da Xue Xue Bao 2013 Feb 18; 45(1):27-32
- CONCLUSIONS: The initial periodontal therapy can significantly improve periodontal clinical parameters and HbA1c control, but the effect on venous fasting blood glucose was not revealed yet. In addition, initial periodontal therapy can also intervene serum phosphorus,calcium-phosphorus ratio, and the metabolism of lipid.
- Thermodynamics of the GTP-GDP-operated conformational switch of selenocysteine-specific translation factor SelB. [Journal Article]
- JBJ Biol Chem 2012 Aug 10; 287(33):27906-12
- SelB is a specialized translation factor that binds GTP and GDP and delivers selenocysteyl-tRNA (Sec-tRNA(Sec)) to the ribosome. By analogy to elongation factor Tu (EF-Tu), SelB is expected to contro...
SelB is a specialized translation factor that binds GTP and GDP and delivers selenocysteyl-tRNA (Sec-tRNA(Sec)) to the ribosome. By analogy to elongation factor Tu (EF-Tu), SelB is expected to control the delivery and release of Sec-tRNA(Sec) to the ribosome by the structural switch between GTP- and GDP-bound conformations. However, crystal structures of SelB suggested a similar domain arrangement in the apo form and GDP- and GTP-bound forms of the factor, raising the question of how SelB can fulfill its delivery function. Here, we studied the thermodynamics of guanine nucleotide binding to SelB by isothermal titration calorimetry in the temperature range between 10 and 25 °C using GTP, GDP, and two nonhydrolyzable GTP analogs, guanosine 5'-O-(γ-thio)triphosphate (GTPγS) and guanosine 5'-(β,γ-imido)-triphosphate (GDPNP). The binding of SelB to either guanine nucleotide is characterized by a large heat capacity change (-621, -467, -235, and -275 cal × mol(-1) × K(-1), with GTP, GTPγS, GDPNP, and GDP, respectively), associated with compensatory changes in binding entropy and enthalpy. Changes in heat capacity indicate a large decrease of the solvent-accessible surface area in SelB, amounting to 43 or 32 amino acids buried upon binding of GTP or GTPγS, respectively, and 15-19 amino acids upon binding GDP or GDPNP. The similarity of the GTP and GDP forms in the crystal structures can be attributed to the use of GDPNP, which appears to induce a structure of SelB that is more similar to the GDP than to the GTP-bound form.
- Entropy-driven binding of picomolar transition state analogue inhibitors to human 5'-methylthioadenosine phosphorylase. [Journal Article]
- BBiochemistry 2011 Nov 29; 50(47):10408-17
- Human 5'-methylthioadenosine phosphorylase (MTAP) links the polyamine biosynthetic and S-adenosyl-l-methionine salvage pathways and is a target for anticancer drugs. p-Cl-PhT-DADMe-ImmA is a 10 pM, s...
Human 5'-methylthioadenosine phosphorylase (MTAP) links the polyamine biosynthetic and S-adenosyl-l-methionine salvage pathways and is a target for anticancer drugs. p-Cl-PhT-DADMe-ImmA is a 10 pM, slow-onset tight-binding transition state analogue inhibitor of the enzyme. Titration of homotrimeric MTAP with this inhibitor established equivalent binding and independent catalytic function of the three catalytic sites. Thermodynamic analysis of MTAP with tight-binding inhibitors revealed entropic-driven interactions with small enthalpic penalties. A large negative heat capacity change of -600 cal/(mol K) upon inhibitor binding to MTAP is consistent with altered hydrophobic interactions and release of water. Crystal structures of apo MTAP and MTAP in complex with p-Cl-PhT-DADMe-ImmA were determined at 1.9 and 2.0 Å resolution, respectively. Inhibitor binding caused condensation of the enzyme active site, reorganization at the trimer interfaces, the release of water from the active sites and subunit interfaces, and compaction of the trimeric structure. These structural changes cause the entropy-favored binding of transition state analogues. Homotrimeric human MTAP is contrasted to the structurally related homotrimeric human purine nucleoside phosphorylase. p-Cl-PhT-DADMe-ImmA binding to MTAP involves a favorable entropy term of -17.6 kcal/mol with unfavorable enthalpy of 2.6 kcal/mol. In contrast, binding of an 8.5 pM transition state analogue to human PNP has been shown to exhibit the opposite behavior, with an unfavorable entropy term of 3.5 kcal/mol and a favorable enthalpy of -18.6 kcal/mol. Transition state analogue interactions reflect protein architecture near the transition state, and the profound thermodynamic differences for MTAP and PNP suggest dramatic differences in contributions to catalysis from protein architecture.
- Antiproliferative Activity of Cinnamomum cassia Constituents and Effects of Pifithrin-Alpha on Their Apoptotic Signaling Pathways in Hep G2 Cells. [Journal Article]
- EBEvid Based Complement Alternat Med 2011; 2011:492148
- Cinnamaldehyde (Cin), cinnamic acid (Ca) and cinnamyl alcohol (Cal), major constituents of Cinnamomum cassia, have been shown to possess antioxidant, anti-inflammatory, anticancer and other activitie...
Cinnamaldehyde (Cin), cinnamic acid (Ca) and cinnamyl alcohol (Cal), major constituents of Cinnamomum cassia, have been shown to possess antioxidant, anti-inflammatory, anticancer and other activities. In this study, our aim was to evaluate the antiproliferative activity of these compounds in human hepatoma Hep G2 cells and examine the effects of pifithrin-alpha (PFTα; a specific p53 inhibitor) on their apoptotic signaling transduction mechanism. The antiproliferative activity was measured by XTT assay. Expression of apoptosis-related proteins was detected by western blotting. Results showed that at a concentration of 30 μM, the order of antiproliferative activity in Hep G2 cells was Cin > Ca > Cal. Cin (IC(50) 9.76 ± 0.67 μM) demonstrated an antiproliferative potency as good as 5-fluorouracil (an anti-cancer drug; IC(50) 9.57 ± 0.61 μM). Further studies on apoptotic mechanisms of Cin showed that it downregulated the expression of Bcl-(XL), upregulated CD95 (APO-1), p53 and Bax proteins, as well as cleaving the poly (ADP-ribose) polymerase (PARP) in a time-dependent pattern. PFTα pre-incubation significantly diminished the effect of Cin-induced apoptosis. It markedly upregulated the anti-apoptotic (Bcl-(XL)) expression and downregulated the pro-apoptotic (Bax) expression, as well as effectively blocking the CD95 (APO-1) and p53 expression, and PARP cleavage in Cin-treated cells. This study indicates that Cin was the most potent antiproliferative constituent of C. cassia, and its apoptotic mechanism in Hep G2 cells could be mediated through the p53 induction and CD95 (APO-1) signaling pathways.
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- Antiatherogenic effect of isoflavones in ovariectomized apolipoprotein e-deficient mice. [Journal Article]
- JAJ Agric Food Chem 2007 Oct 31; 55(22):8967-71
- The consumption of isoflavone-containing foods such as soybean and soybean products has been reported to have beneficial effects on the cardiovascular system in postmenopausal women. The present stud...
The consumption of isoflavone-containing foods such as soybean and soybean products has been reported to have beneficial effects on the cardiovascular system in postmenopausal women. The present study was carried out to examine the mechanism underlying the beneficial effects of isoflavones in apolipoprotein (apo) E-deficient mice subjected to ovarian resection. Compared with sham-operated mice, ovariectomized mice had a larger arterial lesion area in the aortic root. Feeding the ovariectomized mice an isoflavone-containing diet (0.055 mg/kJ of total isoflavones/cal of diet) reduced the size of these lesions more than did feeding them with an isoflavone-free diet. Neither ovariectomy nor diet had a significant effect on the concentration of cholesterol in serum and urinary levels of isoprostanes, which are biomarkers for oxidative stress in vivo. The ovariectomized mice showed a greater increase in mRNA abundance for monocyte chemoattractant protein (MCP)-I in the aorta and in the level of nitric oxide (NO) secreted by peritoneal macrophages in culture than did the sham-operated mice. The isoflavone-containing diet lowered the MCP-I expression and the NO secretion more than did the isoflavone-free diet. These results suggest that dietary isoflavones confer an antiatherogenic effect by preventing the activation of macrophages due to the removal of ovaries.