Shotgun protein sequencing with meta-contig assembly

Area of Science:

• Proteomics
• Bioinformatics
• Mass Spectrometry

Background:

• De novo sequencing of unknown proteins from tandem mass (MS/MS) spectra is challenging due to incomplete fragmentation and low signal-to-noise ratios.
• Conventional algorithms produce short, low-accuracy sequences, limiting applications for antibodies or unsequenced genomes.
• Shotgun Protein Sequencing (SPS) improves accuracy by assembling spectra into contigs but still requires homologous protein matching for full-length reconstruction.

Purpose of the Study:

• To develop a de novo sequencing method that overcomes the limitations of SPS by assembling contigs without relying on homologous protein sequences.
• To achieve accurate reconstruction of long de novo protein sequences from MS/MS data.

Main Methods:

• Developed the Meta-SPS algorithm to overlap and assemble SPS contigs.
• Utilized low and high-resolution CID and high-resolution HCD MS/MS spectra.
• Demonstrated Meta-SPS using distinct MS/MS datasets from separate enzymatic digestions.

Main Results:

• Meta-SPS successfully assembled de novo contig sequences up to 100 amino acids long.
• Achieved over 97% accuracy in de novo sequencing.
• Enabled accurate protein sequencing without prior knowledge of homologous sequences.

Conclusions:

• Meta-SPS significantly advances de novo protein sequencing capabilities, particularly for poorly annotated proteomes.
• The method provides long, highly accurate sequences, expanding the scope of protein identification and characterization.
• Further research can explore the impact of MS/MS acquisition settings on de novo sequencing limitations.