Catalysis-associated conformational changes revealed by human CD38 complexed with a non-hydrolyzable substrate analog
Qun Liu1, Irina A Kriksunov, Christelle Moreau
1MacCHESS, Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14853, USA.
Cyclic ADP-ribose (cADPR) hydrolysis by CD38 is structurally detailed using a non-hydrolyzable analog, N1-cIDPR. This reveals enzyme-substrate conformational changes crucial for calcium signaling and drug design.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Cyclic ADP-ribose (cADPR) is a key calcium messenger regulating physiological functions.
- CD38 enzyme controls endogenous cADPR levels through synthesis and hydrolysis.
- Understanding cADPR hydrolysis mechanisms is vital for cellular signaling research.
Purpose of the Study:
- To elucidate the structural basis of cADPR hydrolysis by CD38.
- To investigate the role of the catalytic residue Glu-226 in cADPR hydrolysis.
- To characterize enzyme-substrate interactions using a novel analog.
Main Methods:
- Utilized a non-hydrolyzable cADPR analog, N1-cIDPR.
- Determined crystal structures of CD38-N1-cIDPR complexes via X-ray crystallography (1.7 and 1.76 Å resolution).
- Analyzed enzyme and substrate conformational changes during catalysis.
Main Results:
- N1-cIDPR inhibits CD38-catalyzed cADPR hydrolysis (IC50 = 0.26 mM).
- N1-cIDPR forms hydrogen bonds with the catalytic residue Glu-226.
- Structural data confirm catalysis-associated conformational changes in both CD38 and cADPR.
- Identified key enzyme residues (Glu-146, Asp-147, Trp-125) facilitating Michaelis complex formation.
Conclusions:
- The study provides a detailed atomic resolution model of the CD38-cADPR binary complex.
- Confirms the proposed catalytic model for cADPR hydrolysis.
- Structural insights can guide the design of novel cADPR analogs for therapeutic applications.
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