近日，國(guó)際著名雜志PNAS在線刊登了美國(guó)研究人員的最新研究成果“Structural engineering of a phage lysin that targets Gram-negative pathogens”,，文章中,，研究者揭示了一種工程改造的細(xì)胞溶解酶可以殺滅革蘭氏陰性致病菌。
噬菌體是一種可以感染細(xì)菌具有多產(chǎn)能力的病毒,，隨著噬菌體感染細(xì)菌最終可以引起大多數(shù)細(xì)菌的死亡,。自從噬菌體在1910年被發(fā)現(xiàn)以來(lái),，其用于治療細(xì)菌感染的潛力被許多科學(xué)家不斷發(fā)掘著,；當(dāng)然目前來(lái)說(shuō)噬菌體療法剛剛起步,，但是隨著小分子抗生素的價(jià)格越來(lái)越便宜而且治療細(xì)菌感染的效力越來(lái)越大，噬菌體療法就慢慢被忽略了,。
近年來(lái)隨著抗生素耐藥菌株的不斷出現(xiàn),，噬菌體療法又被提上議程，這使得科學(xué)家們對(duì)于此療法的前景抱有很大希望,。已有研究者使用稱為細(xì)胞溶解素的噬菌體衍生蛋白質(zhì)作為制劑來(lái)清除體內(nèi)的革蘭氏陰性致病菌感染,，如治療肺炎鏈球菌和炭疽桿菌感染等。
在文章中,，研究者分離觀察到了鼠疫桿菌毒素蛋白的晶體結(jié)構(gòu),，并且揭示了如何對(duì)噬菌體溶解素進(jìn)行工程操作來(lái)殺滅革蘭氏陰性菌，這種鼠疫桿菌毒素蛋白稱為鼠疫巴氏菌素,，屬于細(xì)菌毒素蛋白家族的一種,。研究中，研究者Susan報(bào)道說(shuō),，他們首次使用了工程改造的細(xì)胞溶解素來(lái)直接殺滅革蘭氏陰性菌,，研究者識(shí)別并分離出了鼠疫巴氏菌素的結(jié)構(gòu)，并且用其引導(dǎo)并改造工程化的雜種細(xì)胞溶解素,。鼠疫巴氏菌素包括兩個(gè)結(jié)構(gòu)域：結(jié)合FyuA的靶點(diǎn)（FyuA是鼠疫巴氏菌素的外膜蛋白,，扮演著其受體的作用）；另一個(gè)結(jié)構(gòu)域?yàn)榻到怆木厶?。這種工程改造的雜種細(xì)胞溶解素包括T4溶菌酶,，一種原型的溶菌素，可以吸附至FyuA的靶點(diǎn)結(jié)構(gòu)域上,。研究者表示這種雜種細(xì)胞溶解素（細(xì)胞溶解酶）可以橫過(guò)細(xì)菌的外膜蛋白,，并且最終殺死細(xì)菌菌體。而且這種細(xì)胞溶解酶的行為并不受Pim影響,，Pim是一種鼠疫桿菌產(chǎn)生的蛋白質(zhì),，可以抑制肽多糖降解酶類。因此研究者的研究結(jié)果最終揭示了其可以抑制并且殺死表達(dá)FyuA的革蘭氏陰性菌菌體,。（生物谷Bioon.com）
doi:10.1073/pnas.1203472109
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Structural engineering of a phage lysin that targets Gram-negative pathogens
Petra Lukacika, Travis J. Barnarda, Paul W. Kellerb, Kaveri S. Chaturvedic, Nadir Seddikia, James W. Fairmana, Nicholas Noinaja, Tara L. Kirbya, Jeffrey P. Hendersonc, Alasdair C. Stevenb, B. Joseph Hinnebuschd, and Susan K. Buchanana,1
Bacterial pathogens are becoming increasingly resistant to antibiotics. As an alternative therapeutic strategy, phage therapy reagents containing purified viral lysins have been developed against Gram-positive organisms but not against Gram-negative organisms due to the inability of these types of drugs to cross the bacterial outer membrane. We solved the crystal structures of a Yersinia pestis outer membrane transporter called FyuA and a bacterial toxin called pesticin that targets this transporter. FyuA is a β-barrel membrane protein belonging to the family of TonB dependent transporters, whereas pesticin is a soluble protein with two domains, one that binds to FyuA and another that is structurally similar to phage T4 lysozyme. The structure of pesticin allowed us to design a phage therapy reagent comprised of the FyuA binding domain of pesticin fused to the N-terminus of T4 lysozyme. This hybrid toxin kills specific Yersinia and pathogenic E. coli strains and, importantly, can evade the pesticin immunity protein (Pim) giving it a distinct advantage over pesticin. Furthermore, because FyuA is required for virulence and is more common in pathogenic bacteria, the hybrid toxin also has the advantage of targeting primarily disease-causing bacteria rather than indiscriminately eliminating natural gut flora.
