Structural transformation of a hydrogel-forming cell division protein ZapB of multidrug resistant Klebsiella pneumoniae with small molecules.

Septal ring assembly protein ZapB (EMR18431.1) is involved in Z-ring formation, and nucleoid segregation during the bacterial cell division . It promotes cell division in the initial stages of the cell cycle through direct interaction with FtsZ, thus stimulating Z-ring assembly. The ZapB inhibition can make bacterial cell susceptible to primary antibiotics, and therefore considered as an important approach for adjuvent therapy against MDR bacterial infections. Hence in the current study, ZapB protein of multidrug resistant Klebsiella pneumoniae was cloned, and expressed in E. coli system. To understand its role, and to assess the mechanism of ZapB activation, the characteristic microstructure of ZapB filament network were analyzed by scanning electron microscopy (SEM). ZapB self assembles into long filaments in a concentration dependent manner, and arranges themselves in meshworks, leading to polymeric forms. Furthermore, the effects of 26 compounds, including US-FDA approved drugs, and synthetic compounds of various chemical classes, on the filament formation ability of ZapB were studied by using SEM, and in silico methods. Among them, 5 compounds were found to disrupt the microstructure of ZapB, including trimethoprim (1), amikacin sulphate (2), hydroquinone (3), tobramycin (4), and bis(4-hydroxyphenyl) sulfide (5). Quantitative analysis demonstrated that morphological parameters of ZapB filament were significantly reduced following - treatment with test compounds. Among them, compound 2 showed the most pronounced effect, reducing filament length to 35.48 ± 21.55 µm (mean ± SD), whereas untreated ZapB filaments have an average length of 205.38 ± 89.34 µm, and broadest average diameter of 23.67 ± 7.71 µm. Molecular docking studies further predicted their non-covalent interactions with ZapB protein via hydrogen bond, salt bridges, and aromatic hydrogen bonds. Better understanding of the hydrogelation mechanism of ZapB, and its disruption is important for the development of new inhibitors of the cell division of bacteria. This can, therefore, serve as an important approach for the multi-target treatment of bacterial infections.