Comparison of self-processing of foot-and-mouth disease virus leader proteinase and porcine reproductive and respiratory syndrome virus leader proteinase nsp1α

•We examine self-processing of the leader protease of foot-and-mouth disease virus.•NMR analysis strongly supports intramolecular self-processing.•Self-processing is a dynamic process with no stable complex.•Structural comparison with nsp1α of PRRSV which forms stable intramolecular complex.•Subdomain orientation explains differences in stability of intramolecular complexes.

The foot-and-mouth disease virus leader proteinase (Lbpro) cleaves itself off the nascent viral polyprotein. NMR studies on the monomeric variant Lbpro L200F provide structural evidence for intramolecular self-processing. 15N-HSQC measurements of Lbpro L200F showed specifically shifted backbone signals in the active and substrate binding sites compared to the monomeric variant sLbpro, 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 nsp1α, with a papain-like fold like Lbpro, stably binds its own CTE. Parts of the β-sheet domains but none of the α-helical domains of Lbpro and nsp1α superimpose; consequently, the α-helical domain of nsp1α is oriented differently relative to its β-sheet domain. This provides a large interaction surface for the CTE with the globular domain, stabilising the intramolecular complex. Consequently, self-processing inactivates nsp1α but not Lbpro.

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