Crystal Structure of Periplasmic Domain of YejM from Klebsiella pneumoniae.

YejM (also known as PbgA) is an essential inner membrane protein in Gram-negative bacteria that plays a central role in maintaining outer membrane lipid homeostasis. Although the periplasmic domain of YejM has been structurally characterized in Escherichia coli and Salmonella enterica, structural information from other clinically important pathogens remains limited. Here, we report the crystal structure of the periplasmic domain of YejM from Klebsiella pneumoniae. The structure reveals a conserved α/β fold that closely resembles previously reported YejM structures, with strong structural and sequence conservation across Enterobacteriaceae. Comparative analyses demonstrate that key architectural features and conserved residues implicated in lipid sensing are preserved in K. pneumoniae, supporting a conserved functional role for YejM across species. These findings extend current structural knowledge of YejM to an important opportunistic pathogen and reinforce the view that the molecular mechanism underlying YejM-mediated regulation of outer membrane lipid homeostasis is evolutionarily conserved among Gram-negative bacteria.