Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway and an attractive target for drug design. The crystal structure of Streptococcus mutants purine nucleoside phosphorylase（Smu PNP） has bee...Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway and an attractive target for drug design. The crystal structure of Streptococcus mutants purine nucleoside phosphorylase（Smu PNP） has been solved by molecular replacement at 1.80 resolution and refined to R factors of 19.9%/23.7%（Rcryst/Rfree） . Sequence alignment and structural comparison show that Smu PNP has more similarity with PNPs isolated from human and malarial sources than the bacterial PNPs. The structure complexed with hypoxanthine（HPA） and sulfate ion was solved at 2.24A resolution and refined to R factors of 21.6%/24.1%（Rcryst/Rfree） . It is interesting to note that the resulting electron density indicated the product,HPA,presents in the active site although inosine was included in the crystallization mixture with Smu PNP. Asn233 and Glu191 are the important residues for ligand binding and recognition. Comparison with PNPs from different species gives detailed information about binding of small molecules on the active site,which is important for the studies of enzymatic mechanism and rational design of specific inhibitors for PNPs.展开更多
Abstract:Objective To study the pathogen of root surface caries in the elderly. Methods Plaque samples from the experimental group and the control group were collected. After culturing in selective and non-selective m...Abstract:Objective To study the pathogen of root surface caries in the elderly. Methods Plaque samples from the experimental group and the control group were collected. After culturing in selective and non-selective media, the different bacteria were isolated. The counts and the positive rates of total bacteria, porphyromonas group, pervotella group, streptococcus mutants group, actinomyces group and lactobacillus group were compared.Results The counts of total bacteria, streptococcus mutants, actinomyces and lactobacillus of the experimental group were higher than those of the control group. The positive rates of actinomyces and lactobacillus of the experimental group were significantly higher than those of the control group. Conclusion Actinomyces and lactobacillus are the main related pathogens of root surface caries in the elderly.展开更多
基金Supported by the National Natural Science Foundation of China (30530190 to XDS and 30700115 to NY)
文摘Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway and an attractive target for drug design. The crystal structure of Streptococcus mutants purine nucleoside phosphorylase（Smu PNP） has been solved by molecular replacement at 1.80 resolution and refined to R factors of 19.9%/23.7%（Rcryst/Rfree） . Sequence alignment and structural comparison show that Smu PNP has more similarity with PNPs isolated from human and malarial sources than the bacterial PNPs. The structure complexed with hypoxanthine（HPA） and sulfate ion was solved at 2.24A resolution and refined to R factors of 21.6%/24.1%（Rcryst/Rfree） . It is interesting to note that the resulting electron density indicated the product,HPA,presents in the active site although inosine was included in the crystallization mixture with Smu PNP. Asn233 and Glu191 are the important residues for ligand binding and recognition. Comparison with PNPs from different species gives detailed information about binding of small molecules on the active site,which is important for the studies of enzymatic mechanism and rational design of specific inhibitors for PNPs.
文摘Abstract:Objective To study the pathogen of root surface caries in the elderly. Methods Plaque samples from the experimental group and the control group were collected. After culturing in selective and non-selective media, the different bacteria were isolated. The counts and the positive rates of total bacteria, porphyromonas group, pervotella group, streptococcus mutants group, actinomyces group and lactobacillus group were compared.Results The counts of total bacteria, streptococcus mutants, actinomyces and lactobacillus of the experimental group were higher than those of the control group. The positive rates of actinomyces and lactobacillus of the experimental group were significantly higher than those of the control group. Conclusion Actinomyces and lactobacillus are the main related pathogens of root surface caries in the elderly.
