Multidimensional Solid-State Nuclear Magnetic Resonance of a Functional Multiprotein Chemoreceptor Array.

Area of Science:

• Structural Biology
• Biochemistry
• Microbiology

Background:

• The bacterial chemoreceptor complex is crucial for signal detection and chemotaxis.
• The detailed molecular mechanisms underlying chemoreceptor complex function remain incompletely understood.
• Understanding these mechanisms is vital for deciphering bacterial navigation and response strategies.

Purpose of the Study:

• To investigate the structural changes in bacterial chemoreceptor complexes during signaling.
• To establish a foundation for detailed molecular studies of chemotaxis signal transduction.
• To utilize solid-state NMR for analyzing large, functional receptor arrays.

Main Methods:

• Assembled native-like functional arrays of aspartate receptor cytoplasmic fragment (CF) with CheA and CheW.
• Employed uniformly (13)C- and (15)N-enriched samples for solid-state NMR spectroscopy.
• Performed homo- and heteronuclear two-dimensional NMR experiments to assign residue types and secondary structures.

Main Results:

• Achieved residue-type assignments for 90% of the aspartate receptor cytoplasmic fragment within large arrays (>13.8 MDa).
• NMR spectral data align with structure-based chemical shift predictions, indicating predominantly α-helical secondary structures.
• Observed narrow line widths and spectral changes upon freezing suggest sample homogeneity and immobilization suitable for NMR.

Conclusions:

• The study successfully demonstrates the feasibility of using solid-state NMR to study large, functional chemoreceptor arrays.
• Initial structural insights reveal predominantly α-helical regions and a disordered C-terminal tail in the receptor fragment.
• These findings pave the way for detailed structural and dynamic investigations into bacterial chemotaxis signaling mechanisms.