Lamb Kristen M, Lombardo Michael N, Alverson Jeremy, Priestley Nigel D, Wright Dennis L, Anderson Amy C
Department of Pharmaceutical Sciences, University of Connecticut, Storrs, Connecticut, USA.
Department of Chemistry, University of Montana, Missoula, Montana, USA.
Antimicrob Agents Chemother. 2014 Dec;58(12):7484-91. doi: 10.1128/AAC.03555-14. Epub 2014 Oct 6.
Resistance to the antibacterial antifolate trimethoprim (TMP) is increasing in members of the family Enterobacteriaceae, driving the design of next-generation antifolates effective against these Gram-negative pathogens. The propargyl-linked antifolates are potent inhibitors of dihydrofolate reductases (DHFR) from several TMP-sensitive and -resistant species, including Klebsiella pneumoniae. Recently, we have determined that these antifolates inhibit the growth of strains of K. pneumoniae, some with MIC values of 1 μg/ml. In order to further the design of potent and selective antifolates against members of the Enterobacteriaceae, we determined the first crystal structures of K. pneumoniae DHFR bound to two of the propargyl-linked antifolates. These structures highlight that interactions with Leu 28, Ile 50, Ile 94, and Leu 54 are necessary for potency; comparison with structures of human DHFR bound to the same inhibitors reveal differences in residues (N64E, P61G, F31L, and V115I) and loop conformations (residues 49 to 53) that may be exploited for selectivity.
在肠杆菌科成员中，对抗菌性抗叶酸药物甲氧苄啶（TMP）的耐药性正在增加，这推动了针对这些革兰氏阴性病原体的下一代抗叶酸药物的设计。炔丙基连接的抗叶酸药物是几种对TMP敏感和耐药菌株（包括肺炎克雷伯菌）的二氢叶酸还原酶（DHFR）的强效抑制剂。最近，我们确定这些抗叶酸药物能抑制肺炎克雷伯菌菌株的生长，有些菌株的最低抑菌浓度（MIC）值为1μg/ml。为了进一步设计针对肠杆菌科成员的强效和选择性抗叶酸药物，我们确定了肺炎克雷伯菌DHFR与两种炔丙基连接的抗叶酸药物结合的首个晶体结构。这些结构突出表明，与亮氨酸28、异亮氨酸50、异亮氨酸94和亮氨酸54的相互作用对效力至关重要；与结合相同抑制剂的人DHFR结构进行比较，发现残基（N64E、P61G、F31L和V115I）和环构象（残基49至53）存在差异，这些差异可用于实现选择性。
