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Abstract：
Argyrins are natural products with antibacterial activity against Gram-negative pathogens, such as Pseudomonas aeruginosa, Burkholderia multivorans, and Stenotrophomonas maltophilia We previously showed that argyrin B targets elongation factor G (FusA). Here, we show that argyrin B activity against P. aeruginosa PAO1 (MIC = 8 μg/ml) was not affected by deletion of the MexAB-OprM, MexXY-OprM, MexCD-OprJ, or MexEF-OprN efflux pump. However, argyrin B induced expression of MexXY, causing slight but reproducible antagonism with the MexXY substrate antibiotic ciprofloxacin. Argyrin B activity against Escherichia coli increased in a strain with nine tolC efflux pump partner genes deleted. Complementation experiments showed that argyrin was effluxed by AcrAB, AcrEF, and MdtFX. Argyrin B was inactive against Acinetobacter baumannii Differences between A. baumannii and P. aeruginosa FusA proteins at key residues for argyrin B interaction implied that natural target sequence variation impacted antibacterial activity. Consistent with this, expression of the sensitive P. aeruginosa FusA1 protein in A. baumannii conferred argyrin susceptibility, whereas resistant variants did not. Argyrin B was active against S. maltophilia (MIC = 4 μg/ml). Spontaneous resistance occurred at high frequency in the bacterium (circa 10-7), mediated by mutational inactivation of fusA1 rather than by amino acid substitutions in the target binding region. This strongly suggested that resistance occurred at high frequency through loss of the sensitive FusA1, leaving an alternate argyrin-insensitive elongation factor. Supporting this, an additional fusA-like gene (fusA2) is present in S. maltophilia that was strongly upregulated in response to mutational loss of fusA1.
摘要：
Argyrins是对革兰氏阴性病原体具有抗菌活性的天然产物，比如铜绿假单胞菌,Burkholderiamultivorans,和嗜麦芽窄食单胞菌我们先前表明，argyrinB靶向延伸因子G（FusA）。这里,我们表明，argyrinB对铜绿假单胞菌PAO1的活性（MIC=8μg/ml）不受MexAB-OprM缺失的影响，MexXY-OprM,MexCD-OprJ,或MexEF-OprN外排泵。然而,argyrinB诱导MexXY表达，引起与MexXY底物抗生素环丙沙星的轻微但可重复的拮抗作用。在缺失9个tolC外排泵伴侣基因的菌株中，ArgyrinB对大肠杆菌的活性增加。补充实验表明，AcrAB清除了argyrin，AcrEF,MdtFXArgyrinB对鲍曼不动杆菌无活性鲍曼不动杆菌和铜绿假单胞菌FusA蛋白在argyrinB相互作用的关键残基上的差异暗示天然靶序列变异影响抗菌活性。与此一致，敏感的铜绿假单胞菌FusA1蛋白在鲍曼不动杆菌中的表达赋予了精氨酸敏感性，而抗性变体没有。ArgyrinB对嗜麦芽窄食链球菌有活性(MIC=4μg/ml)。自发耐药在细菌中发生频率很高（大约10-7），由fusA1的突变失活而不是由靶结合区的氨基酸取代介导。这强烈表明，由于失去敏感的FusA1，在高频率下发生了电阻，留下了另一个对精氨酸不敏感的伸长因子。支持这一点,另外的fusA样基因(fusA2)存在于嗜麦芽嗜血杆菌中,其响应于fusA1的突变丢失而被强烈上调。
