噬菌體是一種可以感染細菌具有多產(chǎn)能力的病毒，隨著噬菌體感染細菌zui終可以引起大多數(shù)細菌的死亡。自從噬菌體在1910年被發(fā)現(xiàn)以來，其用于治療細菌感染的潛力被許多科學家不斷發(fā)掘著;當然目前來說噬菌體療法剛剛起步，但是隨著小分子抗生素的價格越來越便宜而且治療細菌感染的效力越來越大，噬菌體療法就慢慢被忽略了。
近年來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，這使得科學家們對于此療法的前景抱有很大希望。已有研究者使用稱為細胞溶解素的噬菌體衍生蛋白質(zhì)作為制劑來清除體內(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)，并且揭示了如何對噬菌體溶解素進行工程操作來殺滅革蘭氏陰性菌，這種鼠疫桿菌毒素蛋白稱為鼠疫巴氏菌素，屬于細菌毒素蛋白家族的一種。研究中，研究者Susan報道說，他們使用了工程改造的細胞溶解素來直接殺滅革蘭氏陰性菌，研究者識別并分離出了鼠疫巴氏菌素的結(jié)構(gòu)，并且用其引導并改造工程化的雜種細胞溶解素。鼠疫巴氏菌素包括兩個結(jié)構(gòu)域：結(jié)合FyuA的靶點(FyuA是鼠疫巴氏菌素的外膜蛋白，扮演著其受體的作用);另一個結(jié)構(gòu)域為降解肽聚糖。這種工程改造的雜種細胞溶解素包括T4溶菌酶，一種原型的溶菌素，可以吸附至FyuA的靶點結(jié)構(gòu)域上。研究者表示這種雜種細胞溶解素(細胞溶解酶)可以橫過細菌的外膜蛋白，并且zui終殺死細菌菌體。而且這種細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zui終揭示了其可以抑制并且殺死表達FyuA的革蘭氏陰性菌菌體。
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 indiscriminay eliminating natural gut flora.