This study was aimed at predicting and analyzing the structural and functional properties of the persistence-associated secretory protein PaaX in Mycobacterium tuberculosis(M.tb),identifying its interacting partners,and elucidating its biological roles.Bioinformatics analysis revealed that PaaX comprises 240 amino acids with a molecular mass of 26.54 kDa(C1158H1866N354O334S14).The protein lacks transmembrane domains but contains a signal peptide.Its secondary structure is dominated by α-helices(53.33%),fol-lowed by random coils(36.25%)and extended strands(10.42%),thereby forming a homotetrameric spatial configuration.Potential PaaX-interacting proteins,including Rv0406c,EchA4,EchA5,HsaE,FadE8,LpqP,and End,were predicted.These candidate genes and the paaX gene were cloned into bacterial two-hybrid vectors and co-transformed into Escherichia coli BTH101 cells.Colony PCR and sequencing confirmed the accuracy of the recombinant constructs.Bacterial two-hybrid assays demonstrated direct interac-tions of PaaX with EchA4,HsaE,FadE8,and LpqP.Moreover,gradient dilution experiments indicated that the strongest binding af-finity occurred between PaaX and EchA4.AlphaFold 3 modeling further validated these interactions,thus providing high-confidence predictions of binding interfaces.Our findings revealed that PaaX,a secreted α-helix-rich protein,engages in specific interactions with key metabolic enzymes(EchA4,HsaE,and FadE8)and a lipoprotein(LpqP),thus suggesting its potential involvement in lipid metabolism,stress adaptation,and host-pathogen interactions.This study provides novel insights into PaaX's contribution to M.tb per-sistence and pathogenicity,and highlights its value as a potential target for tuberculosis diagnostics and therapeutic development.

This study was aimed at predicting and analyzing the structural and functional properties of the persistence-associated secretory protein PaaX in Mycobacterium tuberculosis(M.tb),identifying its interacting partners,and elucidating its biological roles.Bioinformatics analysis revealed that PaaX comprises 240 amino acids with a molecular mass of 26.54 kDa(C1158H1866N354O334S14).The protein lacks transmembrane domains but contains a signal peptide.Its secondary structure is dominated by α-helices(53.33%),fol-lowed by random coils(36.25%)and extended strands(10.42%),thereby forming a homotetrameric spatial configuration.Potential PaaX-interacting proteins,including Rv0406c,EchA4,EchA5,HsaE,FadE8,LpqP,and End,were predicted.These candidate genes and the paaX gene were cloned into bacterial two-hybrid vectors and co-transformed into Escherichia coli BTH101 cells.Colony PCR and sequencing confirmed the accuracy of the recombinant constructs.Bacterial two-hybrid assays demonstrated direct interac-tions of PaaX with EchA4,HsaE,FadE8,and LpqP.Moreover,gradient dilution experiments indicated that the strongest binding af-finity occurred between PaaX and EchA4.AlphaFold 3 modeling further validated these interactions,thus providing high-confidence predictions of binding interfaces.Our findings revealed that PaaX,a secreted α-helix-rich protein,engages in specific interactions with key metabolic enzymes(EchA4,HsaE,and FadE8)and a lipoprotein(LpqP),thus suggesting its potential involvement in lipid metabolism,stress adaptation,and host-pathogen interactions.This study provides novel insights into PaaX's contribution to M.tb per-sistence and pathogenicity,and highlights its value as a potential target for tuberculosis diagnostics and therapeutic development.