Fig. 1: Engineered activation and structural characterization of stabilized TMPRSS2 ectodomain.
From: Structure and activity of human TMPRSS2 protease implicated in SARS-CoV-2 activation
a, Membrane-bound TMPRSS2 zymogen undergoes autocleavage activation at the Arg255-Ile256 peptide bond and the matured enzyme proteolytically processes SARS-CoV-2 Spike protein (magnified) docked to the ACE2 receptor (yellow) to drive membrane fusion. b, Engineered recombinant TMPRSS2 ectodomain (dasTMPRSS2) containing the LDLR-A ___domain, a Class A SRCR ___domain and a C-terminal trypsin-like S1 peptidase (SP) ___domain, features a DDDDK255 substitution to facilitate controlled zymogen activation. Purified, concentrated dasTMPRSS2 can self-activate. The noncatalytic (LDLR-A + SRCR) and catalytic (SP) chains are tethered by a disulfide bond and the activation status can be interrogated by SDS–PAGE under nonreducing and reducing (5% β-mercaptoethanol) conditions. Gel results are consistent with n ≥ 3 independent biological experiments. c, X-ray crystal structure of dasTMPRSS2 pretreated with nafamostat, resulting in phenylguanidino acylation (gray sticks). d, Close-up view of the SP catalytic triad residues (His296, Asp345 and Ser441) and the postactivation Asp440:Ile256 salt bridge showing complete maturation of the protease. Polar contacts are shown as yellow dashed lines. e, The interdomain disulfide (Cys244-Cys365) maintains covalent attachment of the SRCR and SP domains.
