Disruption of histidine biosynthesis in Acinetobacter baumannii by Tubuloside B from Cistanche tubulosa

The alarming rise of multidrug-resistant Acinetobacter baumannii, a WHO priority pathogen causing hospital-acquired infections, demands innovative Antibacterial strategies beyond traditional Antibiotics. With stalled Antibiotic development pipelines, identifying new druggable Bacterial targets and exploring natural product frameworks becomes crucial. This study investigates Histidinol dehydrogenase (HisD), a metalloenzyme catalyzing the terminal step of histidine biosynthesis, as a novel Antibacterial target vital for Bacterial survival. We successfully cloned, expressed, and purified A. baumannii HisD using Ni-NTA affinity chromatography. Structure-based virtual screening of 2000 natural compounds from the Selleckchem database was performed using Glide Docking (Schrödinger Suite 2017-1). Top-scoring ligands underwent 100-ns molecular dynamics simulations and pharmacokinetic profiling. Tubuloside B, a plant-derived glycoside, emerged as the lead compound with exceptional binding affinity (docking score: -13.308 kcal/mol; glide energy: -101.10 kcal/mol) and favourable pharmacokinetic properties, including good gastrointestinal absorption without blood-brain barrier penetration. Experimental validation through surface plasmon resonance confirmed strong binding affinity (KD = 290 nM), while fluorescence quenching verified HisD active site interaction. Antibacterial susceptibility assays demonstrated potent activity against A. baumannii (MIC = 187 μg/mL), with SEM imaging revealing significantly reduced biofilm formation. These findings establish HisD as a viable drug target and highlight Tubuloside B as a promising natural scaffold for drug development. The study emphasizes the relevance of plant-derived bioactives in combating antimicrobial resistance, offering new therapeutic avenues against multidrug-resistant A. baumannii infections.

Acinetobacter baumannii; Antibiotic resistance; Histidinol dehydrogenase; Medicinal biochemistry; Phytochemicals; Therapeutic inhibitors.