Top-down MS, a powerful complement to the high capabilities of proteolysis proteomics

Area of Science:

• Proteomics
• Mass Spectrometry
• Biochemistry

Background:

• Top-down proteomics analyzes intact proteins using mass spectrometry, offering high specificity for characterization and post-translational modifications.
• This approach is more complex than bottom-up proteomics, which analyzes peptides from digested proteins.
• Top-down methods provide more specific data, leading to lower false-positive rates and efficient quantitation of modified isomers.

Purpose of the Study:

• To enhance the capabilities of top-down proteomics for analyzing large proteins.
• To overcome the limitations of molecular ion dissociation in mass spectrometry.
• To improve the characterization of protein sequences and complex post-translational modifications.

Main Methods:

• Utilized electrospray ionization mass spectrometry (ESI MS) for molecular and fragment ion mass data acquisition.
• Employed MS/MS for dissociation of individual protein components separated by ESI MS.
• Implemented 'prefolding dissociation' involving variable thermal and collisional activation post-electrospray.

Main Results:

• Demonstrated successful cleavage of 287 inter-residue bonds in a 1314-residue protein.
• Identified previously unknown disulfide bonds in a 1714-residue protein.
• Corrected sequence predictions for proteins up to 2153 residues (229 kDa).

Conclusions:

• The 'prefolding dissociation' technique significantly extends the applicability of top-down proteomics to larger proteins.
• Top-down mass spectrometry, enhanced by new methods, provides unparalleled detail in protein characterization.
• This advancement allows for more accurate analysis of protein structure, modifications, and sequences, overcoming previous mass limitations.