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Structural asymmetry and intersubunit communication in muscle creatine kinase
Jeffrey F Ohren1, Melisa L Kundracik, Charles L Borders
1Department of Chemistry, The University of Toledo, Toledo, Ohio 43606, USA.
Summary
Rabbit muscle creatine kinase (rmCK) exhibits asymmetric structures, revealing how N-terminal regions regulate enzyme activity and dimerization. Mutations disrupting these regions reduce catalytic function, highlighting their importance in enzyme regulation.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Rabbit muscle creatine kinase (rmCK) is crucial for cellular energy homeostasis.
- Understanding rmCK's catalytic mechanism and regulation is vital for metabolic research.
Purpose of the Study:
- To elucidate the structural basis of rmCK catalysis and regulation.
- To investigate the role of the N-terminal region in rmCK subunit association and activity.
Main Methods:
- X-ray crystallography of a transition-state analog complex of rmCK (R134K mutant) at 1.65 A resolution.
- Site-directed mutagenesis (N-terminal deletion and P20G point mutation) to assess functional impact.
Main Results:
- The study revealed significant structural asymmetry in the rmCK homodimer, with distinct monomer conformations and active site occupancies.
- The N-terminal regions contribute to dimer interface but exhibit conformational differences between subunits.
- Mutations affecting the N-terminus (deletion or P20G) disrupted dimer cohesion, leading to monomer dissociation and reduced catalytic activity.
Conclusions:
- The N-terminal region plays a structural role in rmCK subunit association.
- rmCK N-terminus is mechanistically involved in active-site communication and catalytic regulation.
- Structural asymmetry is key to understanding rmCK's functional regulation.
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