School of Dentistry, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW, 2145, Australia.
Institute of Dental Research, Westmead Centre for Oral Health, Westmead, NSW, 2145, Australia.
Nat Commun. 2018 Oct 5;9(1):4097. doi: 10.1038/s41467-018-06470-0.
Porphyromonas gingivalis is a keystone bacterial pathogen of chronic periodontitis. P. gingivalis is unable to synthesise the porphyrin macrocycle and relies on exogenous porphyrin, including haem or haem biosynthesis intermediates from host sources. We show that under the iron-limited conditions prevailing in tissue environments, P. gingivalis expresses a haemophore-like protein, HusA, to mediate the uptake of essential porphyrin and support pathogen survival within epithelial cells. The structure of HusA, together with titration studies, mutagenesis and in silico docking, show that haem binds in a hydrophobic groove on the α-helical structure without the typical iron coordination seen in other haemophores. This mode of interaction allows HusA to bind to a variety of abiotic and metal-free porphyrins with higher affinities than to haem. We exploit this unusual porphyrin-binding activity of HusA to target a prototypic deuteroporphyrin-metronidazole conjugate with restricted antimicrobial specificity in a Trojan horse strategy that effectively kills intracellular P. gingivalis.
牙龈卟啉单胞菌是慢性牙周炎的关键细菌病原体。牙龈卟啉单胞菌无法合成卟啉大环，依赖于外源性卟啉，包括来自宿主的血红素或血红素生物合成中间体。我们表明，在组织环境中普遍存在的铁限制条件下，牙龈卟啉单胞菌表达一种类似于血红素载体的蛋白 HusA，以介导必需卟啉的摄取，并支持病原体在上皮细胞内的存活。HusA 的结构，以及滴定研究、突变和计算机对接表明，血红素结合在 α-螺旋结构的疏水性凹槽中，而不是在其他血红素载体中常见的典型铁配位。这种相互作用模式允许 HusA 结合各种非生物和无金属卟啉，其亲和力高于血红素。我们利用 HusA 这种不寻常的卟啉结合活性，以 Trojan 马策略靶向一种典型的粪卟啉-甲硝唑缀合物，该缀合物在限制抗菌特异性方面具有高度特异性，可有效杀死细胞内的牙龈卟啉单胞菌。
