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Structural and functional linkages between subunit interfaces in mammalian pyruvate kinase.
J O Wooll1, R H Friesen, M A White
1Department of Human Biological Chemistry and Genetics and the Sealy Center for Structural Biology, The University of Texas Medical Branch, Galveston, TX 77555-0647, USA.
Journal of Molecular Biology
|September 21, 2001
Summary
Mutating rabbit muscle pyruvate kinase (M1-PK) at the Y interface alters its structure, impacting the Z interface. This reveals how subunit interactions regulate enzyme function and allosteric regulation.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Mammalian pyruvate kinase (PK) exists as tissue-specific isozymes with varying allosteric regulation.
- Muscle PK (M1-PK) exhibits hyperbolic kinetics, while kidney PK (M2-PK) shows sigmoidal kinetics.
- Sequence differences between M1-PK and M2-PK are concentrated at inter-subunit interfaces.
Purpose of the Study:
- To investigate the role of inter-subunit interactions in signal transmission within M1-PK.
- To understand the functional and structural connectivity between different interfaces in PK.
- To elucidate how mutations affect allosteric regulation and conformational states.
Main Methods:
- Crystallization and X-ray diffraction of the S402P mutant of M1-PK.
- Structural analysis comparing the mutant to wild-type M1-PK.
- Comparison with previously resolved PK structures.
Main Results:
- The S402P mutation in M1-PK caused backbone conformational changes at the Y interface.
- A salt bridge loss at the Z interface (Asp177:Arg341) was observed.
- Increased rotational flexibility of domain B, containing the active site, correlated with salt bridge loss.
Conclusions:
- Structural linkages exist between the Y and Z interfaces in rabbit M1-PK.
- These linkages mediate the interconversion of enzyme conformational states.
- Inter-subunit interactions are critical for regulating PK allosteric behavior.