Mobility in pyruvate dehydrogenase complexes with multiple lipoyl domains

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Enzymology

Background:

• Pyruvate dehydrogenase (PDH) complexes are crucial metabolic hubs.
• The structure of PDH complexes, particularly the role of lipoyl domains, is key to understanding their function.
• Escherichia coli PDH serves as a model system for studying these large multienzyme complexes.

Purpose of the Study:

• To investigate the structural and dynamic contributions of lipoyl domains within the Escherichia coli PDH complex.
• To correlate the number of lipoyl domains with the overall mobility and catalytic efficiency of the PDH complex.
• To provide insights into the evolutionary rationale for the specific number of lipoyl domains in wild-type PDH.

Main Methods:

• High-field Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• Genetically reconstructed PDH complexes with varying numbers of lipoyl domains (0-9 per E2p subunit) were analyzed.
• NMR spectra were compared to assess differences in domain mobility and signal intensity.

Main Results:

• NMR spectral intensities directly correlated with the number of lipoyl domains present.
• Complexes lacking lipoyl domains showed significantly enhanced signals from the E3-binding domain and its linker.
• The wild-type PDH complex, with three lipoyl domains, exhibited distinct mobility and potentially superior active-site coupling.

Conclusions:

• The number of lipoyl domains significantly influences the dynamic properties of the PDH complex.
• Lipoyl domains contribute to the structural organization and potentially the catalytic efficiency of PDH.
• The findings support a functional advantage for the three-lipoyl domain stoichiometry observed in wild-type E. coli PDH.