Tat-Beclin-1: Molecular Structure
Chemical properties, amino acid sequence, and structural analysis
📌TL;DR
- •Molecular formula: C164H251N57O45
- •Molecular weight: 3028.44 Da
- •Half-life: Not formally characterized in vivo. The L-form is expected to be rapidly degraded by serum proteases. The retro-inverso D-form (Tat-D11) has enhanced resistance to proteolytic degradation and increased in vivo stability, though specific half-life values have not been published.
Amino Acid Sequence
42 amino acids
Formula
C164H251N57O45
Molecular Weight
3028.44 Da
Half-Life
Not formally characterized in vivo. The L-form is expected to be rapidly degraded by serum proteases. The retro-inverso D-form (Tat-D11) has enhanced resistance to proteolytic degradation and increased in vivo stability, though specific half-life values have not been published.
Molecular Structure#
Tat-Beclin-1 is a rationally designed chimeric peptide that combines cell-penetrating and autophagy-inducing functional domains into a single molecule.
Primary Structure#
| Property | Value |
|---|---|
| Full name | Tat-Beclin-1 (Tat-BECN1) |
| L-form sequence (Tat-L11) | YGRKKRRQRRRGGVWNATFHIWHD |
| D-form sequence (Tat-D11) | RRRQRRKKRGYGGDHWIHFTANWV (retro-inverso) |
| Total length | 24 amino acids |
| Approximate molecular weight | ~3,028 Da (L-form) |
| CAS number | 1423821-88-8 |
| Net charge at pH 7.4 | Highly positive (arginine/lysine-rich Tat domain) |
Domain Architecture#
Tat-Beclin-1 consists of three distinct functional domains:
1. HIV-1 Tat Protein Transduction Domain (11 residues)
Sequence: YGRKKRRQRRR
This domain is derived from the HIV-1 Tat protein and functions as a cell-penetrating peptide (CPP). The high density of arginine and lysine residues creates a strongly cationic sequence that enables translocation across cell membranes through interactions with negatively charged membrane phospholipids and glycosaminoglycans.
2. Diglycine Linker (2 residues)
Sequence: GG
A minimal, flexible linker connecting the cell-penetrating and autophagy-inducing domains. Glycine residues provide conformational flexibility while minimizing steric interference between the two functional domains.
3. Beclin 1 Domain (18 residues, aa 267-284)
Sequence: VWNATFHIWHD (C-terminal portion shown)
This domain is derived from a region of beclin 1 that binds to GAPR-1/GLIPR2. Beclin 1 residues 267-284 were identified through screening of beclin 1 fragments for autophagy-inducing activity. This region is also the domain through which HIV-1 Nef protein binds to and inhibits beclin 1-mediated autophagy.
L-Form vs D-Form (Retro-Inverso)#
Two forms of Tat-Beclin-1 are used in research:
| Property | L-Form (Tat-L11) | D-Form (Tat-D11) |
|---|---|---|
| Amino acid chirality | Natural L-amino acids | D-amino acids |
| Sequence direction | N-to-C (normal) | Reversed (retro-inverso) |
| Protease resistance | Low (rapidly degraded) | High (D-amino acids resist proteases) |
| In vivo stability | Low | Enhanced |
| Autophagy induction | Active | Active |
| Primary use | In vitro studies | In vivo studies |
The retro-inverso approach preserves the overall side-chain topology and functional activity while rendering the peptide backbone resistant to endogenous proteases. This is a well-established strategy for improving peptide drug stability.
Size Comparison#
| Peptide | Size | Molecular Weight | Function |
|---|---|---|---|
| Tat-Beclin-1 | 24 amino acids | ~3,028 Da | Autophagy induction |
| Humanin | 24 amino acids | ~2,687 Da | Mitochondrial-derived cytoprotection |
| GHK-Cu | 3 amino acids + Cu | ~403 Da | Wound healing, gene regulation |
| Epitalon | 4 amino acids | ~390 Da | Proposed telomerase activation |
| Vilon | 2 amino acids | ~275 Da | Proposed immune modulation |
At ~3 kDa, Tat-Beclin-1 is substantially larger than most peptide bioregulators but smaller than full proteins, placing it in a size range where cell penetration is achievable with the Tat CPP domain.
Chemical Properties#
Charge and Solubility#
The Tat domain contributes 8 positively charged residues (5 Arg + 3 Lys) at physiological pH, making Tat-Beclin-1 a highly cationic peptide. This positive charge:
- Enables membrane translocation via the Tat CPP mechanism
- Promotes water solubility
- May facilitate electrostatic interactions with negatively charged cellular components
Stability Considerations#
The L-form of Tat-Beclin-1 is susceptible to rapid proteolytic degradation by serum proteases, endopeptidases, and aminopeptidases. In practice:
- In vitro: L-form is adequate for cell culture experiments where exposure time is controlled
- In vivo: The retro-inverso D-form is preferred due to resistance to enzymatic degradation
- Storage: Lyophilized peptide should be stored at -20 degrees C. Reconstituted solutions should be aliquoted and stored frozen to minimize degradation
Target Interaction#
The beclin 1 domain of Tat-Beclin-1 interacts with GAPR-1/GLIPR2, a lipid raft-associated protein on the cytosolic face of the Golgi membrane. Structural studies have characterized the GAPR-1/beclin 1 interaction interface, confirming that Tat-Beclin-1 competes with endogenous beclin 1 for GAPR-1 binding, thereby freeing beclin 1 to activate the autophagy-initiating Class III PI3K complex.
Related Reading#
Frequently Asked Questions About Tat-Beclin-1
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Disclaimer: For educational purposes only. Not medical advice. Read full disclaimer