ATG4B Human

ATG4B is a cysteine protease that belongs to the autophagin protein family. It is also known as Autophagin-1 or APG4B. The protein is encoded by the ATG4B gene located on chromosome 2q37.3 in humans . The human recombinant form of ATG4B is typically produced in E. coli and is a single, non-glycosylated polypeptide chain containing 401 amino acids with a molecular mass of approximately 45.4 kDa .

The primary function of ATG4B is to process the ATG8 family proteins (such as LC3, GABARAP, and GATE-16) by cleaving their C-terminal regions to expose a glycine residue. This processing is crucial for the conjugation of ATG8 proteins to phosphatidylethanolamine (PE), a lipidation step necessary for the formation of autophagosomes .

Autophagy is a highly regulated process that involves the formation of double-membrane vesicles called autophagosomes, which engulf damaged organelles and proteins. These autophagosomes then fuse with lysosomes to degrade their contents. ATG4B plays a dual role in this process:

1. Cleavage of ATG8 Proteins: ATG4B cleaves the C-terminal amino acid of ATG8 family proteins, which is a prerequisite for their conjugation to PE.
2. Deconjugation: ATG4B also removes ATG8 proteins from PE, allowing for the recycling of ATG8 proteins and the disassembly of autophagosomes .

The regulation of autophagy by ATG4B is critical for cellular homeostasis and has implications in various diseases. Reduced levels of autophagy have been associated with several malignant tumors, suggesting a role for autophagy in controlling unregulated cell growth linked to cancer . Additionally, autophagy is involved in neurodegenerative diseases, immune responses, and aging.

The recombinant form of ATG4B is used in research to study its function and role in autophagy. It is produced using recombinant DNA technology, typically in E. coli expression systems. The recombinant protein is purified using chromatographic techniques and is available in various forms, including those with His-tags for easy purification .

Recombinant ATG4B should be stored at -20°C for long-term storage and is stable for up to 12 months under proper storage conditions. It is recommended to avoid repeated freeze-thaw cycles to maintain protein integrity .