Methylation of outer membrane proteins (OMPs) has been implicated in bacterial virulence. Lysine methylation in rickettsial OmpB is correlated with rickettsial virulence, and N- and O-methylations are also observed in virulence-relevant OMPs from several pathogenic bacteria that cause typhus, leptospirosis, tuberculosis, and anaplasmosis. We summarize recent findings on the structure of methylated OmpB, biochemical characterization, and crystal structures of OmpB methyltransferases. Native rickettsial OmpB purified from highly virulent strains contains multiple clusters of trimethyllysine, in contrast with mostly monomethyllysine, and no trimethyllysine is found in an avirulent strain. Crystal structure of the methyltransferases reveals mechanistic insights for catalysis, and a working model is discussed for this unusual post-translational modification.

外膜蛋白（OMPs）的甲基化已被证明与细菌的毒力有关。立克次体OmpB中的赖氨酸甲基化与立克次体毒力相关，并且在与致病性细菌相关的OMPs中也观察到N和O甲基化，这些致病细菌会引起斑疹伤寒，钩端螺旋体病，肺结核和厌氧菌病。我们总结了甲基化OmpB结构，生化特征和OmpB甲基转移酶的晶体结构的最新发现。从高毒力菌株中纯化的天然立克次体OmpB与多甲基赖氨酸相比，含有多簇三甲基赖氨酸，在无毒力菌株中未发现三甲基赖氨酸。甲基转移酶的晶体结构揭示了催化机理，