NMR resonance assignments for sparsely 15N labeled proteins

Area of Science:

• Biochemistry
• Structural Biology
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Determining structures of large proteins or those not suited for bacterial expression is challenging with traditional uniform isotopic labeling (13C, 15N) and Nuclear Overhauser Effects (NOEs).
• Sparse labeling with selected 15N-enriched amino acids offers an alternative by providing diverse backbone structural constraints.
• Current resonance assignment strategies are limited, often requiring uniform labeling or multiple samples with paired isotopic labeling.

Purpose of the Study:

• To develop a novel resonance assignment strategy for protein structure determination.
• To enable structural analysis using a single sample with sparse 15N labeling.
• To overcome limitations of existing NMR methods for challenging protein targets.

Main Methods:

• A new approach correlating amide proton exchange rates is presented.
• Measurements are performed on both the intact protein and its digested, sequenced peptides.
• This method is applicable to a single sample prepared with sparse 15N labeling in selected amino acids.

Main Results:

• The study demonstrates an effective resonance assignment strategy for sparse 15N-labeled proteins.
• The method was successfully applied to determine the structure of the carbohydrate-binding protein Galectin-3.
• This approach facilitates structural studies without uniform labeling or multiple sample preparations.

Conclusions:

• The developed method provides a viable alternative for protein structure determination, especially for difficult targets.
• It simplifies the process by utilizing a single, sparsely labeled sample.
• This advancement has implications for structural biology and understanding protein function.