Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody

Definition and Molecular Target

The Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody is a specialized immunological reagent designed to recognize and bind to the acetylated lysine 33 (K33) residue of ubiquitin and ubiquitin-fusion proteins. This antibody specifically targets the post-translational modification of acetylation at the K33 position in four closely related proteins: UBA52, RPS27A, UBB, and UBC . Ubiquitin is a small regulatory protein found in nearly all eukaryotic cells that serves as a molecular tag for protein degradation and other cellular processes. The four target proteins represent different forms of ubiquitin expression in the genome: UBB and UBC encode polyubiquitin precursors, while UBA52 and RPS27A encode ubiquitin fused to ribosomal proteins L40 and S27a, respectively .

Development and Production

The antibody is typically produced by immunizing rabbits with synthesized peptides derived from human ubiquitin sequences containing the acetylated K33 residue . After immunization, the antibodies are harvested from rabbit serum and undergo affinity purification using epitope-specific immunogen chromatography to isolate antibodies specifically targeting the acetylated K33 residue . This rigorous purification process ensures high specificity and minimal cross-reactivity with other acetylated lysine residues or unmodified ubiquitin. Commercial preparations of this antibody are commonly available in liquid form suspended in phosphate-buffered saline (PBS) containing preservatives such as glycerol, bovine serum albumin (BSA), and sodium azide to maintain stability during storage .

Physical and Chemical Characteristics

The Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody is typically provided as a polyclonal IgG antibody derived from rabbit hosts . The physical characteristics and formulation specifications of commercially available preparations are summarized in the table below:

The antibody maintains its activity and specificity when stored properly, typically at -20°C, with precautions taken to avoid repeated freeze-thaw cycles that could compromise its performance .

Applications and Recommended Dilutions

The Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody has been validated for several research applications, with Western blot (WB) and enzyme-linked immunosorbent assay (ELISA) being the primary recommended techniques . Based on commercial datasheets, the recommended dilutions for various applications are as follows:

Researchers should perform optimization experiments to determine the ideal concentration for their specific experimental conditions, as factors such as sample type, protein expression levels, and detection methods can influence the optimal antibody dilution .

Species Reactivity and Specificity

The antibody demonstrates broad species reactivity, with confirmed detection capabilities in human, mouse, and rat samples . This cross-species reactivity makes the antibody valuable for comparative studies across different model organisms. The antibody specifically recognizes the acetylated lysine 33 residue in the following ubiquitin and ubiquitin-fusion proteins:

• UBA52 (Ubiquitin A-52 residue ribosomal protein fusion product)

• RPS27A (Ubiquitin-40S ribosomal protein S27a)

• UBB (Polyubiquitin-B)

• UBC (Polyubiquitin-C)

The high specificity for the K33 acetylation site enables precise investigation of this particular post-translational modification without interference from other acetylated lysine residues within ubiquitin .

Role in Cellular Signaling Pathways

The acetylation of ubiquitin at lysine 33 has emerged as an important post-translational modification involved in several cellular signaling pathways. Research has revealed that K33 acetylation plays a particularly significant role in T-cell receptor (TCR) signaling. In Jurkat T cells, the E3 ubiquitin ligases CBLB and ITCH have been shown to cooperate in inducing T-cell receptor ζ-chain K33-ubiquitination, which subsequently inhibits ZAP70 phosphorylation . This inhibitory effect represents an important regulatory mechanism in immune cell signaling and activation, potentially influencing immune responses and tolerance.

Additionally, K33 ubiquitination has been implicated in adenosine monophosphate-activated protein kinase (AMPK) signaling pathways . AMPK serves as a cellular energy sensor and regulator, suggesting that K33 modification may contribute to cellular metabolism and energy homeostasis regulation. These findings highlight the diverse roles of K33 modifications in cellular communication and response systems.

Involvement in Protein Degradation and Cellular Processes

K33-linked polyubiquitination has been associated with protein trafficking mechanisms, suggesting roles beyond the canonical protein degradation pathways typically associated with ubiquitination . Recent quantitative proteomics studies have revealed that K33-ubiquitination occurs in response to UV radiation, implicating this modification in cellular stress responses and potentially in DNA damage repair mechanisms .

An important discovery in the field has been the identification of ZRANB1/TRABID (zinc finger RANBP2-type containing 1) as a K29- and K33-specific deubiquitinase (DUB) . The presence of specific enzymatic machinery for removing K33-linked ubiquitin chains further underscores the biological significance of this modification and suggests tight regulation of K33 acetylation in cellular processes.

Interaction with Autophagy Machinery

Research utilizing the PolyUb-FC imaging system has revealed that K33-linked polyubiquitin can be recognized by SQSTM1/p62, an important selective autophagy receptor for ubiquitinated cargo . SQSTM1/p62 is known to regulate various signal transduction pathways and is crucial for T-cell receptor signaling as well as the clearance of ubiquitinated protein aggregates, damaged mitochondria, and ubiquitinated microbes .

Experimental evidence shows that K33-linked polyubiquitin is recruited to the phagophore (autophagosome precursor) via the SQSTM1/p62 UBA domain . Immunoprecipitation studies confirmed that FLAG-SQSTM1/p62 binds to polyubiquitinated ubiquitin, including K33-linked chains. This interaction was further validated by experiments using a MYC-K33-only vector, which demonstrated that SQSTM1/p62 specifically forms complexes with K33-linked polyubiquitin . These findings establish a connection between K33 acetylation and cellular quality control mechanisms, potentially influencing cellular homeostasis and response to stress conditions.

Detection and Visualization Techniques

The Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody serves as a valuable tool for detecting and analyzing acetylated ubiquitin in various experimental contexts. Western blot analysis represents one of the primary applications, allowing researchers to identify acetylated proteins in cell lysates and tissue samples . For Western blot applications, the antibody can detect acetylated ubiquitin and ubiquitin-fusion proteins at dilutions ranging from 1:500 to 1:2000, depending on sample concentration and detection methods .

The antibody has also been validated for ELISA applications, typically at more dilute concentrations (approximately 1:20000) . This allows for quantitative assessment of K33 acetylation levels in various experimental conditions, potentially enabling high-throughput screening approaches.

A novel polyubiquitin imaging system, PolyUb-FC, has been developed to visualize K33-linked polyubiquitin in living cells . This system allows for direct observation of K33-linked chains in cellular contexts, providing spatial and temporal information about this modification that traditional biochemical approaches cannot capture. The combination of PolyUb-FC with antibody-based detection methods offers complementary approaches for studying K33 acetylation in biological systems.

Studying Protein Interactions and Aggregation

The antibody has proven useful in studying the interaction between K33-acetylated proteins and their binding partners. Research has demonstrated that some K33-linked polyubiquitin puncta colocalize with aggresomes, suggesting a role in protein aggregation processes . Furthermore, colocalization studies with SQSTM1/p62 have revealed that K33-linked polyubiquitin can be recognized by this autophagy receptor, potentially influencing the clearance of modified proteins .

Immunoprecipitation experiments using the antibody have helped elucidate the specific binding partners of K33-acetylated proteins. These studies have confirmed interactions between K33-linked polyubiquitin and SQSTM1/p62, providing molecular insights into how this modification may influence protein degradation pathways . Such applications highlight the utility of the antibody in dissecting complex protein interaction networks involving K33 acetylation.

Technical Challenges and Limitations

While the Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody offers valuable research capabilities, certain technical challenges should be considered. Creating K33-linked polyubiquitin chains in vitro remains difficult, complicating the development of positive controls for antibody validation . This limitation has led researchers to employ alternative approaches, such as transfecting cells with K33-only ubiquitin vectors to generate K33-linked chains in vivo.

Additionally, as with all antibody-based detection methods, potential cross-reactivity with similar epitopes must be considered. Though the antibody is designed to be specific for the K33 acetylation site, rigorous controls should be included to ensure specificity, especially when working with complex biological samples containing multiple acetylated proteins.

Relationship to Other Ubiquitin Acetylation Antibodies

The Acetyl-UBA52/RPS27A/UBB/UBC (K33) Antibody is part of a broader family of antibodies targeting various acetylation sites on ubiquitin and ubiquitin-fusion proteins. Related antibodies include those targeting acetylation at K27 and K48 residues (PACO06073 and the antibody mentioned in search result #5, respectively) . These different antibodies allow researchers to specifically track distinct acetylation patterns, potentially revealing site-specific functions of ubiquitin modifications.

While these antibodies target different acetylation sites, they share similar technical specifications, typically being rabbit polyclonal antibodies provided in comparable buffer formulations . The consistent host species and preparation methods facilitate experimental standardization when studying multiple acetylation sites simultaneously, though each antibody requires specific validation for its unique epitope.

Distinguishing Features and Applications

What distinguishes the K33 acetylation antibody is its specificity for modifications that have been implicated in unique biological processes. While K48-linked ubiquitin chains are canonically associated with proteasomal degradation and K63-linked chains with signaling and DNA repair, K33-linked chains appear to serve more specialized functions in T-cell receptor signaling and selective autophagy .

The ability to specifically detect K33 acetylation enables researchers to investigate these specialized pathways without interference from other modifications. This specificity is particularly valuable in untangling the complex "ubiquitin code," wherein different ubiquitin modifications can signal distinct cellular outcomes. By comparing results obtained with different site-specific antibodies, researchers can build a more comprehensive understanding of how various ubiquitin modifications interact and coordinate cellular functions.