msrA encodes an efflux protein in Staphylococcus spp.that confers inducible resistance to macrolides,such as erythromycin(ERY),but not telithromycin(TEL).Thus,msrA+S.aureus remain susceptible to TEL.Production of msrA...msrA encodes an efflux protein in Staphylococcus spp.that confers inducible resistance to macrolides,such as erythromycin(ERY),but not telithromycin(TEL).Thus,msrA+S.aureus remain susceptible to TEL.Production of msrAis regulated by a 320-bp upstream region,presumably by translational attenuation,similar to regulation of erm.We investigated whether ERY could induce TEL resistance in msrA+S.aureus.MICs of ERY and TEL were determined by broth microdilution(BMD).Inducible TEL resistance was detected by a BMD checkerboard panel containing combinations of ERY and TEL and by a D-test where an ERY disk was placed 15mm from a TEL disk on a blood agar plate.Blunting of the TEL zones of inhibition proximal to the ERY disk indicated inducible resistance and no blunting indicated no inducible resistance.Approximately 400bp of the upstream regulatory region and 200bp of msrA were amplified by PCR and sequenced.The TEL MICs for 10 msrA+isolates ranged from 0.06-2g/mL(MIC90=0.25g/mL);ERY MICs were all≥32g/mL.All isolates showed an increase in TEL MICs of>2doubling dilutions(MIC90>4g/mL)in the presence of ERY;All were also positive by D-test.For 9isolates(initial TEL MIC<1g/mL),constitutive TEL resistance was selected by plating cells on Mueller-Hinton agar with 2g/mL TEL.All 9isolates grew on the selective media and were resistant to TEL(MIC ranged 2-8g/mL).Mutation to constitutive resistance occurred at a rate of 8×10-7 to 2.4×10-6.Eight of the 9resistant isolates had a single nucleotide substitution in the upstream regulatory region relative to the parent strain.Specifically,six isolates had a G to T mutation at position-222;one had a C to A mutation at-228;And one had a C to A mutation at-247.Transformation of the msrAgene with above point mutation in regulatory region into S.aureus RN4220conferred the strain resistant(MIC=8g/mL)to the telithromycin while transformants with the wild-type msrAgene remained susceptible(MIC=1g/mL)to telithromycin.展开更多
[Objectives]This study was conducted to understand the structure and function of MsrA protein.[Methods]With Vibrio alginolyticus HY9901 as the object of study,primers were designed to amplify the full-length gene of m...[Objectives]This study was conducted to understand the structure and function of MsrA protein.[Methods]With Vibrio alginolyticus HY9901 as the object of study,primers were designed to amplify the full-length gene of msrA,and its bioinformatics analysis was carried out.[Results]The full length of msrA gene was 639 bp,encoding 212 amino acids,and its theoretical molecular weight was about 23729.60 Da.The protein had a stable structure,and it was hydrophobic overall.The structure of signal peptides at the N terminal of the amino acid sequence was predicted,and it was found that there was no signal peptide cleavage site and no transmembrane region.The amino acid sequence of MsrA contained multiple signal binding sites.Protein subcellular localization showed that MsrA protein was most likely located in the cytoplasm.Homology analysis showed that MsrA of V.alginolyticus had high homology with other Vibrio species,and the highest homology with V.alginolyticus.In the prediction of functional domains,MsrA had the function of methionine sulfoxide reduction.In secondary structure prediction,MsrA contained random coils at a proportion of 46.70%,which was the highest.The similarity between the tertiary structure model of MsrA and template Q87SW6.1.A was 89.15%.PTM analysis showed that MsrA protein had many PTM modification sites such as phosphorylation and glycosylation sites.[Conclusions]This study provides some reference value for further study on the role of MsrA in bacterial antioxidant stress.展开更多
以自主研制的硅微谐振式加速度计(MSRA)为研究对象,针对其驱动电路的带宽测试,设计一种基于锁相环解调电路的带宽测试方案。针对锁相环驱动电路的相位传递函数建立SIMULINK仿真模型,并对闭环回路模型进行分析。在锁相环的输入端口加载...以自主研制的硅微谐振式加速度计(MSRA)为研究对象,针对其驱动电路的带宽测试,设计一种基于锁相环解调电路的带宽测试方案。针对锁相环驱动电路的相位传递函数建立SIMULINK仿真模型,并对闭环回路模型进行分析。在锁相环的输入端口加载由现场可编程门阵列(FPGA)产生的激励信号,等效为外界加速度频率变化下的锁相环输入信号,由基于锁相环的解调电路读出加速度计驱动电路的输出幅值,该带宽测试模型与MSRA实际测试情况一致。实验结果表明:MSRA锁相环驱动电路的实测+3 d B的带宽值为210 Hz,与模型仿真得到的216 Hz基本吻合。该测试方法具有精度高、易实施、成本低等特点,可满足锁相环驱动电路的带宽测试需求。展开更多
文摘msrA encodes an efflux protein in Staphylococcus spp.that confers inducible resistance to macrolides,such as erythromycin(ERY),but not telithromycin(TEL).Thus,msrA+S.aureus remain susceptible to TEL.Production of msrAis regulated by a 320-bp upstream region,presumably by translational attenuation,similar to regulation of erm.We investigated whether ERY could induce TEL resistance in msrA+S.aureus.MICs of ERY and TEL were determined by broth microdilution(BMD).Inducible TEL resistance was detected by a BMD checkerboard panel containing combinations of ERY and TEL and by a D-test where an ERY disk was placed 15mm from a TEL disk on a blood agar plate.Blunting of the TEL zones of inhibition proximal to the ERY disk indicated inducible resistance and no blunting indicated no inducible resistance.Approximately 400bp of the upstream regulatory region and 200bp of msrA were amplified by PCR and sequenced.The TEL MICs for 10 msrA+isolates ranged from 0.06-2g/mL(MIC90=0.25g/mL);ERY MICs were all≥32g/mL.All isolates showed an increase in TEL MICs of>2doubling dilutions(MIC90>4g/mL)in the presence of ERY;All were also positive by D-test.For 9isolates(initial TEL MIC<1g/mL),constitutive TEL resistance was selected by plating cells on Mueller-Hinton agar with 2g/mL TEL.All 9isolates grew on the selective media and were resistant to TEL(MIC ranged 2-8g/mL).Mutation to constitutive resistance occurred at a rate of 8×10-7 to 2.4×10-6.Eight of the 9resistant isolates had a single nucleotide substitution in the upstream regulatory region relative to the parent strain.Specifically,six isolates had a G to T mutation at position-222;one had a C to A mutation at-228;And one had a C to A mutation at-247.Transformation of the msrAgene with above point mutation in regulatory region into S.aureus RN4220conferred the strain resistant(MIC=8g/mL)to the telithromycin while transformants with the wild-type msrAgene remained susceptible(MIC=1g/mL)to telithromycin.
基金Supported National Natural Science Foundation of China(32073015)Undergraduate Training Program for Innovation and Entrepreneurship of Guangdong Ocean University(CXXL2024007)+2 种基金Undergraduate Innovation Team of Guangdong Ocean University(CCTD201802)Postgraduate Education Innovation Program of Guangdong Ocean University(No.202446)Postgraduate Education Innovation Program of Guangdong Province(YJYH[2022]1).
文摘[Objectives]This study was conducted to understand the structure and function of MsrA protein.[Methods]With Vibrio alginolyticus HY9901 as the object of study,primers were designed to amplify the full-length gene of msrA,and its bioinformatics analysis was carried out.[Results]The full length of msrA gene was 639 bp,encoding 212 amino acids,and its theoretical molecular weight was about 23729.60 Da.The protein had a stable structure,and it was hydrophobic overall.The structure of signal peptides at the N terminal of the amino acid sequence was predicted,and it was found that there was no signal peptide cleavage site and no transmembrane region.The amino acid sequence of MsrA contained multiple signal binding sites.Protein subcellular localization showed that MsrA protein was most likely located in the cytoplasm.Homology analysis showed that MsrA of V.alginolyticus had high homology with other Vibrio species,and the highest homology with V.alginolyticus.In the prediction of functional domains,MsrA had the function of methionine sulfoxide reduction.In secondary structure prediction,MsrA contained random coils at a proportion of 46.70%,which was the highest.The similarity between the tertiary structure model of MsrA and template Q87SW6.1.A was 89.15%.PTM analysis showed that MsrA protein had many PTM modification sites such as phosphorylation and glycosylation sites.[Conclusions]This study provides some reference value for further study on the role of MsrA in bacterial antioxidant stress.
文摘以自主研制的硅微谐振式加速度计(MSRA)为研究对象,针对其驱动电路的带宽测试,设计一种基于锁相环解调电路的带宽测试方案。针对锁相环驱动电路的相位传递函数建立SIMULINK仿真模型,并对闭环回路模型进行分析。在锁相环的输入端口加载由现场可编程门阵列(FPGA)产生的激励信号,等效为外界加速度频率变化下的锁相环输入信号,由基于锁相环的解调电路读出加速度计驱动电路的输出幅值,该带宽测试模型与MSRA实际测试情况一致。实验结果表明:MSRA锁相环驱动电路的实测+3 d B的带宽值为210 Hz,与模型仿真得到的216 Hz基本吻合。该测试方法具有精度高、易实施、成本低等特点,可满足锁相环驱动电路的带宽测试需求。
