Eliminylation: a post-translational modification catalyzed by phosphothreonine lyases

We propose the classification of a protein post-translational modification, eliminylation, based on the recently delineated mechanism of the Shigella OspF and Salmonella SpvC phosphothreonine lyases. These bacterial type-III secretion-system virulence factors are injected into eukaryotic cells and inhibit signalling by irreversibly inactivating mitogen-activated protein kinases (MAPKs). Remarkably, they employ an unusual β-elimination reaction, removing the phosphate from phosphothreonine and converting it into dehydrobutyrine (an alkene). Eliminylated cysteine can also be produced by decarboxylation and eliminylated serine and threonine by dehydration; these residues are found in the eye lens and in bacterial lantibiotics. We postulate that eliminylation might be a widespread regulatory modification, and we propose the use of phosphothreonine lyases as in vivo MAPK inhibitors both therapeutically and to investigate MAPK signalling regulation.