<i>In silico</i> analysis of the γ-carbonic anhydrase EcoCAγ from <i>Enterobacteria</i> : assessing the role of the 72-residue N-terminal extension

The γ-class carbonic anhydrase EcoCAγ, reported in <i>Escherichia coli</i> in 2022, contains a 72-residue N-terminal extension absent in the canonical YrdA isoform. A genomic analysis confirmed that the full-length EcoCAγ is conserved (95-100% identity) across multiple <i>E. coli</i> and <i>Shigella</i> strains but is not present in the laboratory strain K-12. A full-length trimeric model was generated using AlphaFold-Multimer and subjected to molecular dynamics simulations in aqueous and membrane environments. In membrane conditions, the N-terminal segment maintained an extended α-helical conformation, whereas in aqueous solution it underwent compaction and self-association. Throughout all simulations, the trimeric assembly and the geometry of the catalytic site remained preserved. No disruption of the active-site architecture was observed under either condition. These simulations provide structurally resolved observations of the environment-dependent behavior of the N-terminal region and its effect on the conformational dynamics of the EcoCAγ trimer.