Sandhu Padmani, Akhter Yusuf
School of Life Sciences, Central University of Himachal Pradesh, District - Kangra, Himachal Pradesh 176206, India.
School of Life Sciences, Central University of Himachal Pradesh, District - Kangra, Himachal Pradesh 176206, India.
J Inorg Biochem. 2017 May;170:75-84. doi: 10.1016/j.jinorgbio.2017.02.013. Epub 2017 Feb 14.
Iron is an essential metal ion required for the various physiological activities of bacteria. The pathogenic bacteria remain dependent on the host cell for their iron requirements and evolved with specialized scavenging machinery in the form of iron chelating siderophores. Mycobacterium tuberculosis has two types of siderophore molecules, mycobactin and carboxymycobactin. These are synthesized inside bacterial cells and need to be transported outside by specialized membrane associated proteins. MmpL5-MmpS5 (mycobacterial membrane protein large5-mycobacterial membrane protein small5) complex has been linked to the export of non-ferrated siderophores to extracellular environment but the precise molecular mechanism involved was largely unknown. We have investigated the association of MmpL5 with mycobactin synthesis and transport associated proteins using system wide protein-protein interaction network. Insights of mycobactin transport mechanism by MmpL5-MmpS5 complex was explored using docking and molecular dynamics simulations. The MmpL5 has association with many proteins with reported roles in iron acquisition or mycobactin biosynthesis. The molecular dynamics simulation analysis after mycobactin docking into MmpL5 binding pockets showed that at cytoplasmic binding site, mycobactin could move towards the central channel of efflux pump and at periplasmic binding site towards the periplasm. MmpL5 was observed to carry out uptake of mycobactin from the cytoplasm and its release into the periplasmic space and MmpS5 was found to facilitate the periplasmic release of mycobactin and enhancement in the transport function of MmpL5. The mycobactin export is an attractive target for drug discovery and it may be carried out by inhibiting the MmpL5 protein's transport function.
铁是细菌各种生理活动所必需的金属离子。病原菌的铁需求仍依赖于宿主细胞,并进化出了以铁螯合铁载体形式存在的专门 scavenging 机制。结核分枝杆菌有两种铁载体分子,分枝杆菌素和羧基分枝杆菌素。这些分子在细菌细胞内合成,需要通过专门的膜相关蛋白运输到细胞外。MmpL5-MmpS5(分枝杆菌膜蛋白大5-分枝杆菌膜蛋白小5)复合物与非铁化铁载体向细胞外环境的输出有关,但其中涉及的精确分子机制在很大程度上尚不清楚。我们利用全系统蛋白质-蛋白质相互作用网络研究了MmpL5与分枝杆菌素合成及运输相关蛋白的关联。通过对接和分子动力学模拟探索了MmpL5-MmpS5复合物运输分枝杆菌素的机制。MmpL5与许多在铁获取或分枝杆菌素生物合成中具有报道作用的蛋白质有关联。分枝杆菌素对接至MmpL5结合口袋后的分子动力学模拟分析表明,在细胞质结合位点,分枝杆菌素可向流出泵的中央通道移动,在周质结合位点则向周质移动。观察到MmpL5从细胞质摄取分枝杆菌素并将其释放到周质空间,发现MmpS5促进分枝杆菌素在周质的释放并增强MmpL5的运输功能。分枝杆菌素的输出是药物发现的一个有吸引力的靶点,可通过抑制MmpL5蛋白的运输功能来实现。