Title : Crystal structures of
TAFI elucidate the inactivation mechanism of activated
TAFI : a novel mechanism for
enzyme autoregulation
Abstract :
- Thrombin-activatable fibrinolysis inhibitor ( TAFI ) is a pro-metallocarboxypeptidase that can be proteolytically activated (TAFIa)
- TAFIa is unique among carboxypeptidases in that it spontaneously inactivates with a short half-life, a property that is crucial for its role in controlling blood clot lysis
- We studied the intrinsic instability of TAFIa by solving crystal structures of TAFI , a TAFI inhibitor (GEMSA) complex and a quadruple TAFI mutant (70-fold more stable active enzyme )
- The crystal structures show that TAFIa stability is directly related to the dynamics of a 55-residue segment ( residues 296-350 ) that includes residues of the active site wall
- Dynamics of this flap are markedly reduced by the inhibitor GEMSA, a known stabilizer of TAFIa, and stabilizing mutations
- Our data provide the structural basis for a model of TAFI auto-regulation: in zymogen TAFI the dynamic flap is stabilized by interactions with the activation peptide
- Release of the activation peptide increases dynamic flap mobility and in time this leads to conformational changes that disrupt the catalytic site and expose a cryptic thrombin-cleavage site present at Arg302
- This represents a novel mechanism of enzyme control that enables TAFI to regulate its activity in plasma in the absence of specific inhibitors
Output (sent_index, trigger,
protein,
sugar,
site):
Output(Part-Of) (sent_index,
protein,
site):
- 1. Thrombin-activatable fibrinolysis inhibitor, pro
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):