Methyl groups as probes for proteins and complexes in in-cell NMR experiments

Area of Science:

• Biochemistry
• Biophysics
• Structural Biology

Background:

• Studying large intracellular protein complexes with in-cell Nuclear Magnetic Resonance (NMR) is challenging.
• Slow tumbling rates of large proteins lead to unobservable backbone resonances, hindering analysis.

Purpose of the Study:

• To develop a novel methodology for observing protein components within large intracellular complexes using in-cell NMR.
• To overcome the limitations of slow tumbling rates that obscure backbone resonances.

Main Methods:

• Implementing selective labeling of methyl groups, which exhibit improved relaxation properties.
• Comparing various in-cell labeling strategies on model proteins: calmodulin, NmerA, and FKBP.
• Utilizing [(13)C]methyl group labeling on methionine and alanine residues.

Main Results:

• The developed methodology successfully overcomes the challenge of unobservable backbone resonances.
• Selective [(13)C]methyl labeling on methionine and alanine demonstrated excellent sensitivity.
• Low background signals were achieved with this cost-effective labeling approach.

Conclusions:

• Selective methyl group labeling is a viable strategy for in-cell NMR studies of large protein complexes.
• This technique enhances sensitivity and reduces costs, making complex intracellular protein analysis more accessible.
• The findings pave the way for studying protein dynamics and interactions within their native cellular environment.