Structural characterization of an essential lipoprotein of Mycoplasma pneumoniae

Abstract Mycoplasma pneumoniae is a human pathogen causing atypical community-acquired pneumonia. It is a model for a minimal cell, known for its non-canonical use of surface proteins for host-cell adhesion through ectodomain shedding and antigenic variation to evade the host cell immune response. Mpn444 is an essential mycoplasma surface protein implicated in both processes. It is one of 46 lipoproteins of M. pneumoniae , none of which have been structurally or functionally characterized. Here, we report the structure of Mpn444 at 3.04 Å as well as the molecular architecture of the trimeric Mpn444 complex. Our experimental structure displays striking similarity to structure predictions of several other essential lipoproteins in M. pneumoniae and other related Mycoplasma species, suggesting it to have a specialized and conserved function. The essentiality and involvement of Mpn444 in host immune evasion makes our structure a target for the development of new treatment strategies against mycoplasma infections.