Human coronavirus 229E 3C-like proteinase (3CLpro) (3CLpro)

Human coronavirus 229E 3C-like proteinase (3CLpro), also known as the main protease (Mpro), is an essential enzyme for the replication of HCoV-229E, a common cold-causing virus [6, 13]. It is a cysteine protease that functions as a homodimer to cleave the viral polyproteins pp1a and pp1ab at eleven distinct sites [7, 15]. This proteolytic processing releases functional non-structural proteins that are vital for the assembly of the viral replication-transcription complex [6, 8]. The enzyme utilizes a catalytic dyad of His41 and Cys144 and exhibits a unique substrate preference for glutamine at the P1 position, which is not shared by human proteases [4, 10]. This distinct specificity makes 3CLpro a primary target for antiviral therapy, as inhibitors can be designed to be highly selective with minimal host toxicity [4, 8]. Drugs such as nirmatrelvir and experimental compounds like GC376 target the active site to prevent viral maturation and spread [3, 4]. Beyond its role in replication, 3CLpro also aids in viral pathogenesis by cleaving host proteins like NEMO to suppress the innate immune response [18]. Consequently, 3CLpro remains a focal point for developing broad-spectrum antivirals against both endemic and emerging coronaviruses [1, 10].

Other names

Main protease [2, 4]Mpro [4, 6]nsp5 [6, 7]3CL protease [3, 7]C30 endopeptidase [7]

Covalent inhibition of the catalytic cysteine residue (Cys144) [4, 10]