Middle East respiratory syndrome coronavirus main protease (MERS-CoV 3CLpro) (MERS-CoV 3CLpro)

The Middle East respiratory syndrome coronavirus main protease (MERS-CoV 3CLpro), also known as nsp5, is a critical enzyme for the replication and life cycle of the MERS-CoV virus [1, 10]. It is a cysteine protease that functions as a homodimer, utilizing a conserved Cys-His catalytic dyad to cleave the large viral polyproteins (pp1a and pp1ab) at eleven distinct sites [4, 7]. This proteolytic processing is essential for the release of mature non-structural proteins that form the viral replication-transcription complex [2, 12]. Because 3CLpro recognizes a unique substrate sequence, specifically preferring Glutamine at the P1 position, which is not typically utilized by human host proteases, it is considered a high-value target for the development of specific antiviral therapies [8, 15]. Drugs targeting this protease, such as the broad-spectrum inhibitor GC376 and various peptidomimetics like MK-7845, aim to block the active site or interfere with the enzyme's dimerization, thereby halting viral replication and reducing the severity of the infection [2, 8, 16]. Unlike some other coronaviruses, the MERS-CoV 3CLpro exists in a monomer-dimer equilibrium and is a relatively weakly associated dimer, which can influence the potency and design of potential inhibitors [10, 16]. Given the high mortality rate associated with MERS-CoV infections, 3CLpro remains a primary focus for the development of direct-acting antivirals [1, 14].

Other names

3C-like proteaseMpronsp5Non-structural protein 5C30 endopeptidaseMERS-CoV Mpro

Inhibition of viral polyprotein cleavage by targeting the catalytic Cys-His dyad, thereby preventing the maturation of non-structural proteins essential for the assembly of the viral replication-transcription complex [2, 5, 13].