Establishing the role of novel mutations within AdeRS using homology modelling that cause carbapenem resistance in Acinetobacter baumannii and study the binding patterns of AdeABC with carbapenems and PAβN using molecular docking. (March 2022)

• Record Type: Journal Article
• Authors: Roy, S.; Hazra, S.; Basu, S.
• Is Part Of: International journal of infectious diseases. Volume 116(2022)Supplement
• Page Start: S13
• Publication Date: 2022-03
• Subjects: Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2021.12.032
• Languages: English
• ISSNs: 1201-9712

Abstract

Abstract : Purpose: The study was undertaken to establish the role of novel mutations within AdeRS (regulator of efflux pump AdeABC) associated with overexpression of AdeABC, hence cause carbapenem resistance among Acinetobacter baumannii . In addition, the study was designed to understand the possible atomic level interactions between carbapenems with AdeABC and molecular mechanism of efflux pump inhibition by PAβN (Efflux pump Inhibitor). Methods & Materials: MIC of carbapenems was checked with and without PAβN among A. baumannii (n=56) causing neonatal septicaemia. Overexpression of AdeABC was determined by q-RT PCR. Mutations within AdeRS was determined by sequencing and their role was established using predictive modelling based 3D structure analysis. Protein-substrate interaction studies were performed using molecular docking to understand the binding pattern of FDA approved carbapenems and PAβN in three binding sites (periplasmic, proximal, distal) of AdeB. Results: Exposure of the carbapenem-resistant A. baumannii (CRABs) to PAβN resulted in a decrease in the MICs of carbapnems among 39% of isolates (15/38). Overall, 29% (11/38) of CRAB showed overexpression of AdeB. Mutations within AdeS (GLY186 VAL, SER188 PHE, GLU121 LYS, VAL255 ILE) and AdeR (VAL120 ILE, ALA136 VAL) were detected among which three novel mutations (GLY186 VAL, SER188 PHE, GLU121 LYS) were found to be associated with overexpression of AdeABC established by homology modelling. Our study mechanistically shows how these mutations prevent the phospho-transfer to AdeR which inhibit the binding of AdeR to the Inter Cistronic Space and hence, cause overexpression of efflux pump. Moreover, molecular docking indicates less binding of carbapenems and PAβN at distal site as compared to other sites. However, PAβN was found to block the carbapenem interacting residues in AdeB which indicates its role as a competitive inhibitor of AdeB substrates. Conclusion: Novel mutations within AdeRS are reported for the first time along with their role in AdeB overexpression using predictive 3D modelling. In addition, the study is first time reporting the illustrative demonstration of molecular interaction between AdeB, carbapenems and PAβN. This study revealed the key residues of AdeB that interact with carbapenems as well as PAβN that helping us to understand the molecular reasoning of inhibition as well as creating a future platform for designing novel inhibitors.