Abstract

As the executors of biological activities, proteins do not retain fixed functions after synthesis. Post-translational modifications (PTMs) are dynamic chemical alterations that modulate protein properties without changing their amino acid sequences, acting as crucial "molecular switches" to expand functional diversity. PTMs play indispensable roles in cellular regulation, disease pathogenesis, and drug development. This article systematically outlines the definition, biological significance, and major types of PTMs, summarizes core research methodologies, and briefly introduces ANTBIO’s comprehensive solutions tailored for PTM studies.

1. What Are Post-Translational Modifications?

PTMs refer to a series of enzymatic chemical modifications that proteins undergo after being synthesized in ribosomes. These modifications do not alter the primary amino acid sequence of proteins but profoundly influence their three-dimensional structure, biological activity, subcellular localization, and stability. As a key mechanism for precise cellular regulation, PTMs enable rapid adjustments to protein function in response to internal and external cues, analogous to equipping proteins with tunable "molecular switches."

2. Biological Significance of PTMs

l  Regulation of biological processes: PTMs are involved in all essential cellular activities, including signal transduction, metabolic regulation, and gene expression.

l  Adaptation to environmental changes: When cells encounter stress (e.g., hypoxia, oxidative stress), PTMs rapidly reprogram protein functions to enhance cellular adaptability. For example, phosphorylation activates hypoxia-inducible factor-1 (HIF-1) under hypoxic conditions, regulating gene expression to adapt to a low-oxygen environment. Ubiquitination attaches ubiquitin chains to proteins, which can mark proteins for degradation (such as damaged proteins) or alter signal transduction.

l  Disease biomarkers: Abnormal PTM patterns are closely associated with numerous diseases, such as cancer, neurodegenerative disorders, and autoimmune diseases. For example, Alzheimer's disease and Parkinson's disease involve abnormal phosphorylation or ubiquitination errors of Tau proteins, leading to protein aggregation and neuronal death.

l  Therapeutic targets: Enzymes regulating PTMs (e.g., kinases, deacetylases) have become key targets for drug development, with many targeted therapies approved for clinical use (Nature Reviews Drug Discovery, 2025).

3. Major Types of PTMs

PTMs are classified based on modification mechanisms, with key categories including:

3.1 Classic Modifications

l  Phosphorylation: The most prevalent PTM, primarily targeting serine (Ser), threonine (Thr), and tyrosine (Tyr) residues. It acts as a universal "on/off switch" to regulate enzyme activity and intracellular signaling cascades (Mertins et al., 2016).

l  Acetylation: Mostly occurring on lysine (Lys) residues of histones, it relaxes chromatin structure and promotes gene transcription (Zhai et al., 2025).

l  Ubiquitination: Covalently links ubiquitin molecules to Lys residues, serving as a "degradation tag" to regulate protein turnover or mediate signal transduction (Miller et al., 2009).

3.2 Metabolism-Associated Modifications

l  Lactylation: An emerging research hotspot, predominantly induced under hypoxic conditions and closely linked to tumor metabolism (Zhang et al., 2019).

l  Succinylation: Involved in tricarboxylic acid cycle regulation, bridging metabolic pathways and gene expression (Virág et al., 2020).

l  Crotonylation: Plays critical roles in germ cell development and embryonic differentiation.

3.3 Other Important Modifications

l  Glycosylation: Affects protein folding and cell-cell recognition, essential for immune responses (Macek et al., 2019).

l  Methylation: Regulates transcription factor activity and chromatin structure by modifying Lys or arginine (Arg) residues.

l  Oxidative modification: Reflects cellular oxidative stress status, associated with aging and disease progression.

4. Core Methods for PTM Research

4.1 Western Blot (WB) – Detection of PTM Expression

WB is a widely used method for semi-quantitative PTM detection. The workflow involves protein extraction and quantification, separation via SDS-PAGE, transfer to a membrane, incubation with PTM-specific antibodies, and signal detection to assess PTM expression levels.

4.2 Mass Spectrometry (MS) – Identification and Quantification of PTM Sites

MS is the only technique capable of directly identifying specific PTM sites (e.g., which Ser residue is phosphorylated) and enabling large-scale proteomic analysis, making it ideal for discovering novel PTMs. Key steps include:

1.      Sample preparation: Protein extraction, optional enrichment of modified proteins via immunoaffinity purification (IAP), and treatment with DTT and iodoacetamide.

2.      Digestion: Proteins are cleaved into peptides using trypsin (e.g., ANTBIO MS-grade trypsin, Cat. No. UA070130) at 37°C overnight.

3.      Peptide separation: Fractionation via high-performance liquid chromatography (HPLC), with additional enrichment for modified peptides if needed.

4.      MS analysis: Tandem MS (MS/MS) acquires peptide mass (MS1) and amino acid sequence (MS2) data.

5.      Data interpretation: Database matching with specialized software to confirm PTM sites, types, and quantitative differences across samples.

4.3 Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) – High-Throughput Screening

TR-FRET eliminates background fluorescence interference with high sensitivity and no washing steps, making it suitable for high-throughput screening of inhibitors targeting PTM-regulating enzymes (e.g., kinases). The method can process 96 or 384 samples simultaneously. The workflow includes reagent preparation (Eu³⁺-labeled PTM antibodies and APC-labeled target protein antibodies), assay setup, incubation, fluorescence detection, and data analysis.

5. ANTBIO PTM Research Solutions

ANTBIO offers a comprehensive portfolio of PTM research tools to support diverse experimental needs.

l  Monoclonal antibodies (high specificity and stability),

l  Polyclonal antibodies (strong affinity),

l  Agarose beads (efficient enrichment and purification),

l  Wash buffers (optimized to reduce background), and

l  MS-grade trypsin (suitable for sample preparation).

6. Future Trends

PTM research is evolving toward dynamic, spatiotemporal analysis and clinical translation. Technological advancements such as single-cell PTM proteomics and multi-PTM integration analysis will deepen our understanding of PTM functions. Additionally, PTM-based biomarkers and targeted therapies are expected to play increasingly important roles in precision medicine.

References

1.    Macek, B., et al. (2019). Glycosylation engineering of therapeutic antibodies: Current status and future perspectives. BioDrugs, 33(6), 453-466.

2.    Mertins, P., et al. (2016). Mass spectrometry-based proteomics reveals cancer-associated alterations in protein phosphorylation and ubiquitination. Cell, 164(5), 968-980.

3.    Miller, M. L., et al. (2009). PhosphoSitePlus: a comprehensive resource for investigating the structure and function of experimentally determined post-translational modifications. Nucleic Acids Research, 37(Database issue), D257-D260.

4.    Nature Reviews Drug Discovery. (2025). PTM-regulating enzymes as therapeutic targets. Nature Reviews Drug Discovery, 24(3), 189-208.

5.    Rush, J., et al. (2005). Immunoaffinity profiling of tyrosine phosphorylation in cancer cells. Nature Biotechnology, 23(1), 94-101.

6.    Virág, Z., et al. (2020). Advanced mass spectrometry workflows for PTM analysis. Proteomics, 20(11), e1900244.

7.    Zhang, Y., et al. (2019). Metabolic regulation of gene expression by histone lactylation. Nature, 574(7779), 575-580.

8.    Zhai, Y., et al. (2025). Cysteine carboxyethylation: a novel PTM linking metabolism to autoimmunity. Cell Metabolism, 47(2), 289-302.