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Hydrogen‐deuterium exchange mass spectrometry highlights conformational changes induced by factor XI activation and binding of factor IX to factor XI a
Author(s) -
Bar Barroeta Awital,
Galen Josse,
Stroo Ingrid,
Marquart J. Arnoud,
Meijer Alexander B.,
Meijers Joost C. M.
Publication year - 2019
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.14632
Subject(s) - hydrogen–deuterium exchange , chemistry , zymogen , conformational change , domain (mathematical analysis) , binding domain , biophysics , binding site , prekallikrein , mass spectrometry , biochemistry , stereochemistry , enzyme , chromatography , biology , mathematical analysis , mathematics , kallikrein
Background Factor XI ( FXI ) is a zymogen in the coagulation pathway that, once activated, promotes haemostasis by activating factor IX ( FIX ). Substitution studies using apple domains of the homologous protein prekallikrein have identified that FIX binds to the apple 3 domain of FXI . However, the molecular changes upon activation of FXI or binding of FIX to FXI a have remained largely unresolved. Objectives This study aimed to gain more insight in the FXI activation mechanism by identifying the molecular differences between FXI and FXI a, and in the conformational changes in FXI a induced by binding of FIX . Methods Hydrogen‐deuterium exchange mass spectrometry was performed on FXI , FXI a, and FXI a in complex with FIX . Results Both activation and binding to FIX induced conformational changes at the interface between the catalytic domain and the apple domains of FXI (a)—more specifically at the loops connecting the apple domains. Moreover, introduction of FIX uniquely induced a reduction of deuterium uptake in the beginning of the apple 3 domain. Conclusions We propose that the conformational changes of the catalytic domain upon activation increase the accessibility to the apple 3 domain to enable FIX binding. Moreover, our HDX MS results support the location of the proposed FIX binding site at the beginning of the apple 3 domain and suggest a mediating role in FIX binding for both loops adjacent to the apple 3 domain.