An in Silico Characterisation of ATP-Binding Cassette Transporter Proteins Across Five Endodontic Pathogens:
1Department of Bioengineering and Biotechnology, Birla Institute of Technology, Mesra, Ranchi, Jharkhand, India.
Aim:
ATP-binding cassette (ABC) transporter proteins play pivotal roles in antimicrobial resistance and bacterial virulence. However, their characterisation across major endodontic pathogens remains limited. This study aimed to characterise ABC transporter proteins in silico across five endodontic pathogens and to investigate their implications for antimicrobial resistance and virulence.
Methodology:
Reference genome-predicted proteomes of Enterococcus faecalis, Porphyromonas gingivalis, Fusobacterium nucleatum, Actinomyces naeslundii and Dialister invisus were retrieved from the National Center for Biotechnology Information RefSeq database. ABC transporter proteins were identified using InterProScan and HMMER and assigned to five functional categories based on Pfam domain signatures. Physicochemical parameters were computed and analysed by principal component analysis, the Kruskal-Wallis test and the chi-square test of independence. Domain architecture and phylogenetic analyses were performed using MAFFT, FastTree and Interactive Tree of Life.
Results:
A total of 574 ABC transporter proteins were identified (range: 63-168 per species), with A. naeslundii exhibiting the highest transporter density (55.3 per Mb). Putative multidrug resistance pumps were dominant (78.7%) and were highest in F. nucleatum (87.1%) and E. faecalis (82.2%). Functional category distribution differed significantly between species (χ2 = 22.043, df = 8, p = 0.005). Significant inter-species differences were identified in Grand Average of Hydropathy (GRAVY) score, aromaticity, isoelectric point and instability index (all p < 0.001). BLASTP confirmed the efrAB efflux operon in E. faecalis (EfrA: 99.65%; EfrB: 100.00%) alongside 13 homologue proteins.
Conclusions:
The dominance of putative multidrug resistance pumps, including sequence-confirmed efrAB proteins and 13 homologues in E. faecalis, provides a plausible molecular framework for intrinsic resistance to intracanal medicaments in persistent endodontic infections.
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