Two naturally occurring variants of TAFI (Thr-325 and Ile-325) differ substantially with respect to thermal stability and antifibrinolytic activity of the enzyme.


Abstract

Thrombin-activable fibrinolysis inhibitor (TAFI) is a carboxypeptidase B-like zymogen that is activated to TAFIa by plasmin, thrombin, or the thrombin-thrombomodulin complex. The enzyme TAFIa attenuates clot lysis by removing lysine residues from a fibrin clot. Screening of nine human cDNA libraries indicated a common variation in TAFI at position 325 (Ile-325 or Thr-325). This is in addition to the variation at amino acid position 147 (Ala-147 or Thr-147) characterized previously. Thus, four variants of TAFI having either Ala or Thr at position 147 and either Thr or Ile at position 325 were stably expressed in baby hamster kidney cells and purified to homogeneity. The kinetics of activation of TAFI by thrombin/thrombomodulin were identical for all four variants; however, Ile at position 325 extended the half-life of TAFIa from 8 to 15 min at 37 degrees C, regardless of the residue at position 147. In clot lysis assays with thrombomodulin and the TAFI variants, or with pre-activated TAFI variants, the Ile-325 variants exhibited an antifibrinolytic effect that was 60% greater than the Thr-325 variants. Similarly, in the absence of thrombomodulin, the Ile-325 variants exhibited an antifibrinolytic effect that was 30-50% greater than the Thr-325 variants. In contrast, the variation at position 147 had little if any effect on the antifibrinolytic potential of TAFIa. The increased antifibrinolytic potential of the Ile-325-containing TAFI variants reflects the fact that these variants have an increased ability to mediate the release of lysine from partially degraded fibrin and suppress plasminogen activation. These findings imply that individuals homozygous for the Ile-325 variant of TAFI would likely have a longer lived and more potent TAFIa enzyme than those homozygous for the Thr-325 variant.

Submission Details

ID: eoUTMrqx3

Submitter: Shu-Ching Ou

Submission Date: Oct. 25, 2018, 10:39 a.m.

Version: 1

Publication Details
Schneider M;Boffa M;Stewart R;Rahman M;Koschinsky M;Nesheim M,J Biol Chem (2002) Two naturally occurring variants of TAFI (Thr-325 and Ile-325) differ substantially with respect to thermal stability and antifibrinolytic activity of the enzyme. PMID:11684677
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P
 

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)


Relevant PDB Entries

Structure ID Release Date Resolution Structure Title
4P10 2014-08-13 2.0 pro-carboxypeptidase U In Complex With 5-(3-aminopropyl)-1-propyl-6,7-dihydro-4H-benzimidazole-5-carboxylic acid
3LMS 2010-02-16 2.5 Structure of human activated thrombin-activatable fibrinolysis inhibitor, TAFIa, in complex with tick-derived funnelin inhibitor, TCI.
3D68 2008-07-01 2.8 Crystal structure of a T325I/T329I/H333Y/H335Q mutant of Thrombin-Activatable Fibrinolysis Inhibitor (TAFI-IIYQ)
5HVF 2016-06-22 2.85 Crystal Structure of Thrombin-activatable Fibrinolysis Inhibitor in Complex with an Inhibitory Nanobody (VHH-i83)
5HVH 2016-06-22 3.0 Crystal Structure of Thrombin-activatable Fibrinolysis Inhibitor in Complex with two Inhibitory Nanobodies
5HVG 2016-06-22 3.05 Crystal Structure of Thrombin-activatable Fibrinolysis Inhibitor in Complex with an Inhibitory Nanobody (VHH-a204)
3D66 2008-07-01 3.1 Crystal structure of Thrombin-Activatable Fibrinolysis Inhibitor (TAFI)
3D67 2008-07-01 3.4 Crystal structure of Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) in complex with 2-guanidino-ethyl-mercaptosuccinic acid (GEMSA)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
99.5 Carboxypeptidase B2 Q96IY4 CBPB2_HUMAN