TEM-1 Beta-Lactamase Deep Dive
Antibiotic Resistance Enzyme
Biological Context
TEM-1 β-lactamase is the archetypal class A serine β-lactamase and one of the most prevalent enzymes responsible for bacterial resistance to penicillins. It hydrolyzes the four-membered β-lactam ring of penicillin antibiotics using an active-site serine nucleophile, inactivating them before they can reach their target (the penicillin-binding proteins).
Why it matters: TEM-1 and its descendants (extended-spectrum β-lactamases, ESBLs) are the reason we pair β-lactam antibiotics with inhibitors like clavulanic acid, sulbactam, and tazobactam — the inhibitors covalently disable the β-lactamase and let the antibiotic through. A de novo protein inhibitor of TEM-1 is an interesting academic target: it tests whether we can design high-affinity binders against a well-characterized enzyme active site, and the answer has implications for designing inhibitors of the newer carbapenemases (KPC, NDM) for which we urgently need therapeutics.
The Goal: Design a binder that occludes the active-site cleft of TEM-1. Unlike the cytokine-receptor targets, there’s no natural protein partner to mimic — you’re designing against a small-molecule pocket.
Interactive Structure
The viewer below shows TEM-1 β-lactamase covalently modified by penicillin G (PDB 1FQG captures the acylated reaction intermediate).
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Design Mission
Design a binder that occupies the active-site cleft, preventing β-lactam substrates from docking and being hydrolyzed.
Target Specifications
| Feature | Detail |
|---|---|
| Target Name | TEM-1 β-lactamase |
| PDB ID | 1FQG |
| Target Chain | Chain A |
| Active-site residues (within 5 Å of bound penicillin) | M69, S70, T71, K73, Y105, M129, S130, N132, N170, V216, K234, S235, G236, A237, G238, E239, R243, M270 |
| Catalytic residues | S70 (nucleophile), K73 (general base), S130 (proton shuttle), E166 (deacylation), K234 (substrate positioning) |
| Ω-loop (substrate specificity) | residues 161–179 — these rim the active-site cleft |
These are every TEM-1 residue within 5 Å of the bound penicillin G in 1FQG — in other words, the residues that physically line the substrate-binding pocket. For binder design, these define the surface your binder needs to occlude. The catalytic residues (S70, K73, S130, E166, K234) are deeply buried at the bottom of the cleft; rim residues (the Ω-loop, R243, the 234–240 loop) are more accessible and easier to engage with a binder.
Strategy Tips
- Download PDB
1FQG. - Clean the structure: Keep Chain A, remove water and the bound penicillin (HETATM record
PNM). - Choose a strategy:
- Active-site occlusion: target the residues rimming the pocket (e.g.,
A130,A170,A237,A243) — your binder clamps over the cleft. - Allosteric: target a surface patch away from the active site. More novel but less likely to inhibit; ask whether deformation of the enzyme still blocks substrate access.
- Active-site occlusion: target the residues rimming the pocket (e.g.,
- Validate computationally: After designing a binder, dock a small β-lactam substrate (or use PLACER) into the binder/TEM-1 complex and confirm steric clash — the binder should prevent substrate entry, not just sit nearby.
Reference
- Strynadka, N.C.J. et al. (1992). Molecular structure of the acyl-enzyme intermediate in β-lactam hydrolysis at 1.7 Å resolution. Nature 359, 700–705. doi:10.1038/359700a0 — primary citation for 1FQG.