MigC-BiochemicalRawData-JR.xlsx

To establish colonization within the host, bacterial pathogens like <i>Acinetobacter baumannii</i> must acquire zinc (Zn). To regulate Zn homeostasis, <i>A. baumannii</i> produces COG0523 family proteins, which are predicted to chaperone Zn for metalloprotein incorporation. Bioinformatic analyses identified A1S_0934 as a COG0523 protein in <i>A. baumannii</i>, and yeast two-hybrid screening revealed its interaction with MurD, an essential muramyl ligase. Based on this, we designated A1S_0934 as MurD-interacting GTPase COG0523 (MigC). Here, we demonstrate that MigC functions as a GTPase, with its activity enhanced upon Zn coordination via a conserved CxCC (C = Cys; x = Leu/Ile/Met) motif, forming an S3(N/O) complex. Strains lacking <i>migC</i> (Δ<i>migC</i>) exhibit Zn depletion sensitivity and altered cell wall architecture <i>in vitro</i>. Biochemical and functional assays confirm that MigC interacts with MurD and inhibits its catalytic activity. CRISPRi-mediated <i>murD</i> knockdown reduces <i>A. baumannii</i> fitness and induces filamentation under Zn-limited conditions, a phenotype reversed in Δ<i>migC</i> strains, indicating that MigC suppresses MurD activity in cells. Additionally, Δ<i>migC</i> cells are elongated and more susceptible to ceftriaxone, consistent with compromised cell wall integrity. In a murine pneumonia model, Δ<i>migC</i> exhibits reduced colonization, highlighting the significance of the MigC-MurD interaction during infection. Collectively, these findings suggest that MigC influences cell wall biogenesis, partly through MurD inhibition, underscoring the roles of MigC and MurD in <i>A. baumannii</i> survival and pathogenicity while broadening the functional scope of COG0523 family proteins.