美國愛荷華州立大學(xué)的華裔科學(xué)家Edward Yu領(lǐng)導(dǎo)的團隊最近發(fā)現(xiàn)了細菌體內(nèi)外排泵的結(jié)晶結(jié)構(gòu),，該成果有助于研究人員更好地了解細菌耐藥性機制,，以開發(fā)出新治療方法消除細菌耐藥性。相關(guān)結(jié)果發(fā)表在9月23日的《自然》（Nature）雜志上,。
研究人員首先將大腸桿菌外排泵的組成成分——膜蛋白進行純化,、結(jié)晶，制備含有重金屬銅和銀的細菌樣品及對照組，然后使用X射線結(jié)晶分析技術(shù)對比分析其結(jié)構(gòu),，從而研究出細菌體內(nèi)重金屬外排機制,。
研究人員在文章中特別提到CusA的結(jié)晶結(jié)構(gòu)，CusA是一種內(nèi)膜轉(zhuǎn)運蛋白,，由1,047個氨基酸殘基組成,，屬耐藥結(jié)節(jié)細胞分化（resistance-nodulation-division，RND）超家族,。
“我們希望能徹底研究出這些重金屬外排泵的機制”,，Edward Yu表示，“如此一來,，生物技術(shù)人員便可制備出相應(yīng)抑制劑,，消除細菌的抗生素抗性”。（生物谷Bioon.com）
生物谷推薦英文摘要：
Nature doi:10.1038/nature09395
Crystal structures of the CusA efflux pump suggest methionine-mediated metal transport
Feng Long,Chih-Chia Su,Michael T. Zimmermann,Scott E. Boyken,Kanagalaghatta R. Rajashankar,Robert L. Jernigan& Edward W.
Gram-negative bacteria, such as Escherichia coli, frequently use tripartite efflux complexes in the resistance-nodulation-cell division (RND) family to expel various toxic compounds from the cell1, 2. The efflux system CusCBA is responsible for extruding biocidal Cu(I) and Ag(I) ions3, 4. No previous structural information was available for the heavy-metal efflux (HME) subfamily of the RND efflux pumps. Here we describe the crystal structures of the inner-membrane transporter CusA in the absence and presence of bound Cu(I) or Ag(I). These CusA structures provide new structural information about the HME subfamily of RND efflux pumps. The structures suggest that the metal-binding sites, formed by a three-methionine cluster, are located within the cleft region of the periplasmic domain. This cleft is closed in the apo-CusA form but open in the CusA-Cu(I) and CusA-Ag(I) structures, which directly suggests a plausible pathway for ion export. Binding of Cu(I) and Ag(I) triggers significant conformational changes in both the periplasmic and transmembrane domains. The crystal structure indicates that CusA has, in addition to the three-methionine metal-binding site, four methionine pairs—three located in the transmembrane region and one in the periplasmic domain. Genetic analysis and transport assays suggest that CusA is capable of actively picking up metal ions from the cytosol, using these methionine pairs or clusters to bind and export metal ions. These structures suggest a stepwise shuttle mechanism for transport between these sites.
Molecular, Cellular and Developmental Biology Interdepartmental Graduate Program, Iowa State University, Iowa 50011, USA
Feng Long & Edward W. Yu
Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
Chih-Chia Su & Edward W. Yu
Bioinformatics and Computational Biology Interdepartmental Graduate Program, Iowa State University, Ames, Iowa 50011, USA
Michael T. Zimmermann, Scott E. Boyken, Robert L. Jernigan & Edward W. Yu
NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Building 436E, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
Kanagalaghatta R. Rajashankar
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
Robert L. Jernigan & Edward W. Yu
Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
Edward W. Yu
