Comparison of self-processing of foot-and-mouth disease virus leader proteinase and porcine reproductive and respiratory syndrome virus leader proteinase nsp1α.
The foot-and-mouth disease virus leader proteinase (Lb(pro)) cleaves itself off the nascent viral polyprotein. NMR studies on the monomeric variant Lb(pro) L200F provide structural evidence for intramolecular self-processing. N-15-HSQC measurements of Lb(pro) L200F showed specifically shifted backbone signals in the active and substrate binding sites compared to the monomeric variant sLb(pro), lacking six C-terminal residues. This indicates transient intramolecular interactions between the C-terminal extension (CTE) of one molecule and its own active site. Contrastingly, the porcine reproductive and respiratory syndrome virus (PRRSV) leader proteinase nsp1 alpha, with a papain-like fold like Lb(pro), stably binds its own CTE. Parts of the beta-sheet domains but none of the alpha-helical domains of Lb(pro) and nsp1 alpha superimpose; consequently, the alpha-helical domain of nsp1 alpha is oriented differently relative to its beta-sheet domain. This provides a large interaction surface for the CTE with the globular domain, stabilising the intramolecular complex. Consequently, self-processing inactivates nsp1 alpha but not Lb(pro).