MPM

A number of Mycobacterium tuberculosis lipid antigens have been identified that are presented by group 1 CD1 molecules. CD1c molecules present several mycobacterial or synthetic lipid antigens that share a key chemical motif: methylated alkyl chains. These antigens include synthetic mannosyl phosphodolichols that are structurally related to mycobacterial mannosyl-β1-phosphomycoketide (MPM) and recently described phosphomycoketide (PM). The unusual methyl branches associated with these mycoketide antigens, synthesized by polyketide synthase 12 (pks12), serve as a molecular signature for M. tuberculosis and are required for loading into the CD1c antigen binding groove. MPM binds in the A′ pocket of CD1c and the mannose head group extends out of ligand binding groove to become accessible to a TCR for recognition.