Protein Sequencing: Techniques, Methods, and Applications

Proteins are the executors of cellular activities, and their functions depend on precise amino acid sequences. Once the sequence changes, the structure, interactions, and biological functions of the protein may be significantly affected.Protein SequencingNot only does it help unravel the mechanisms of protein function, but it also plays a foundational role in disease research, antibody development, new drug target screening, and more. Since the mid-20th century, protein sequencing technology has continuously evolved, moving from Edman degradation to high-throughput mass spectrometry platforms, significantly enhancing coverage and data accuracy, and is gradually becoming a core tool in modern proteomics research.

 

I. Main Techniques in Protein Sequencing

1. Edman Degradation

Edman degradation is a chemical sequencing method that sequentially cleaves amino acids from the N-terminal, suitable forsmall peptides or purified proteins. The reaction principle involves using phenyl isothiocyanate (PITC) to selectively label and release the N-terminal amino acid residues, followed by identification through chromatographic methods.

🔸Technical Advantages:

• High precision

• Single sequence analysis, suitable for verifying protein N-terminal

🔸Main Limitations:

• Cannot handle complex mixed samples

• Limited to N-terminal analysis and cannot reveal post-translational modifications

• Low throughput, not suitable for large-scale proteome research

Although its application has significantly decreased after the emergence of high-throughput mass spectrometry, Edman degradation is still used for certainN-terminal closure verificationor recombinant protein identification scenarios.

 

2. Mass Spectrometry

Current protein sequencing mainly relies onMass Spectrometry (MS), where protein samples are enzymatically digested and their peptide fragment spectra are analyzed on high-resolution mass spectrometry platforms to infer the primary structure information of the protein.

🔸Common Mass Spectrometry Sequencing Strategies:

(1) Database-dependent sequencing

This method determines protein sequences by matching MS/MS spectra with theoretical peptide fragments in known protein databases.

▸Process Characteristics:

• Efficient, high degree of automation

• Depends on high-quality databases (e.g., UniProt, NR, Swiss-Prot)

• Can be combined with peptide quantification (e.g., TMT/iTRAQ)

Common algorithm tools include: Mascot, Sequest, MaxQuant, Proteome Discoverer.

(2) De novo sequencing (database-independent)

When the research subject lacks a reliable reference database or aims to discover unknown mutations or variant peptides,de novo sequencingbecomes the preferred method. This method infers amino acid sequences directly from MS/MS spectra without relying on existing databases. Current mainstream de novo tools include: PEAKS, Novor, pNovo, DeepNovo, etc.

(3) Top-down vs. Bottom-up Integration Strategies

Mass spectrometry sequencing is often divided by analysis method into:

• Bottom-up: Proteins are digested into peptides and then analyzed by mass spectrometry, which is the most mainstream approach. Advantages include high sensitivity and throughput, suitable for complex samples.

• Top-down: Directly analyzes the mass spectrometry behavior of intact protein molecules, providing richer structural modification information, but requires higher instrument resolution, suitable for structural proteins, variant proteins, etc.

 

II. Application Scenarios of Protein Sequencing

1. Biomarker Discovery

By comparing the changes in protein sequences in samples from different states (e.g., health vs. disease, treatment group vs. control group),disease-related mutant peptides, new antigens, splice variantsand other potential biomarkers can be identified.

 

2. Disease Mechanism Research

Variations in protein sequences or post-translational modifications are core factors in the occurrence and development of many diseases. Protein sequencing can reveal:

• Phosphorylation sites in kinase regulatory networks

• Histone modifications (acetylation, methylation) and their relationship with gene expression

• Structural and functional abnormalities caused by RNA splicing variants

 

3. Antibody Sequencing and Biopharmaceutical Development

Protein sequencing plays a critical role in the development of antibody-based biopharmaceuticals, primarily applied in:

• Antibody Sequence Confirmation (Heavy Chain/Light Chain Identification)

• Stability Analysis (Sequence Variation Identification, Point Mutation Detection)

• Impurity Protein Detection (Immunogenicity Control)

 

4. Non-model Organism and New Species Research

For non-model organisms lacking genomic information, mass spectrometry combined with de novo sequencing can directly acquire key protein sequence information. Typical applications include:

• Agricultural Biological Germplasm Resource Screening

• Marine Biological Functional Protein Discovery

• Insect and Microbial Natural Product Enzyme Activity Research

 

5. PTM Site Identification and Functional Research

Post-Translational Modifications (PTMs) are core mechanisms for regulating protein functions. Common modifications include:

• Phosphorylation

• Acetylation

• Ubiquitination

• Glycosylation

By using specific enrichment strategies combined with mass spectrometry sequencing, researchers can locate modification sites and quantify modification levels across the entire protein, thereby revealing complex regulatory networks.

 

Protein sequencing serves as a bridge connecting genetic information to protein function. Understanding the technical methods and application areas it encompasses is essential. Biotyper Biotech is dedicated to providing a one-stop protein sequencing solution 'from sample to data', relying on advanced instrument platforms and an experienced mass spectrometry team to offer high-quality, traceable sequencing services to research and industry clients, helping every biological discovery advance further.

 

Biotyper Biotech - Characterization of Biologics, High-Quality Multi-omics Mass Spectrometry Detection Service Provider

 

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