SARS-CoV-2 is the causative agent of COVID-19. The dimeric form of the viral main protease is responsible for the cleavage of the viral polyprotein in 11 sites, including its own N and C-terminus. Herein, we used X-ray crystallography to characterize an immature form of the main protease. We propose that this form preludes the cis-cleavage of N-terminal residues within the dimer, leading to the mature active site. Using fragment screening, we probe new cavities in this form which can be used to guide therapeutic development. Furthermore, we characterized a serine site-directed mutant of the main protease bound to its endogenous N and C-terminal residues during the formation of the tetramer. This quaternary form is also present in solution, suggesting a transitional state during the C-terminal trans-cleavage.

中文翻译：

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SARS-CoV-2主要蛋白酶成熟过程的结晶快照

SARS-CoV-2是COVID-19的病原体。病毒主要蛋白酶的二聚体形式负责11个位点的病毒多蛋白的切割，包括其自身的N和C端。在这里，我们使用X射线晶体学来表征主要蛋白酶的不成熟形式。我们建议这种形式使二聚体中N末端残基的顺式切割成为可能，从而导致成熟的活性位点。使用片段筛选，我们以这种形式探查了新的腔体，可用于指导治疗的发展。此外，我们表征了四聚体形成过程中结合其内源性N和C末端残基的主要蛋白酶的丝氨酸定点突变体。此四元形式也存在于溶液中，表明在C末端反式裂解过程中处于过渡状态。