Plays a role in cell envelope biogenesis, maintenance of cell envelope integrity and membrane homeostasis (PubMed:26391555, PubMed:26454142, PubMed:30368949, PubMed:33431434). Required for the normal cell elongation (PubMed:26391555). May participate in the cell division process (PubMed:26391555). Important for the septum site localization of the essential divisome protein ZipA (PubMed:26391555). (Microbial infection) Probably transports the toxic C-terminal region of CdiA from E.coli strain 869 across the inner membrane to the cytoplasm, where CdiA degrades DNA. Toxin transport is strain-specific, mutations in this gene do not confer resistance to several other tested CdiA toxins. Interact with various proteins involved in cell elongation and cell division (PubMed:26454142). Directly interacts with ZipA (PubMed:26391555). Distributed in the inner membrane through the whole cell. Deletion mutant is shorter than wild type and shows abnormal localization of ZipA, an essential protein of cell division (PubMed:26391555). Deletion mutant is sensitive to low osmolarity (PubMed:26454142). Disruption confers resistance to cellular contact-dependent growth inhibition (CDI) CdiA of E.coli strain 869, but not to a series of other CdiA toxins tested (PubMed:26305955). Cells lacking both yciB and dcrB display pleiotropic defects, including morphological changes, elevated amounts of lipopolysaccharide, membrane vesiculation, reduced proton motive force, accumulation of outer membrane proteins at the inner membrane, and dynamic shrinking and extension of the cytoplasmic membrane accompanied by lysis and cell death (PubMed:30368949). Double mutant also displays a reduction in membrane fluidity and a marked sensitivity to copper ions (PubMed:33431434). It accumulates additional forms of Lpp and shows aberrant localization of Lpp due to inefficient lipid modification at the first step in lipoprotein maturation (PubMed:33431434). Belongs to the YciB family.