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 the deacylation-defective TEM-1 E166N mutant covalently modified by penicillin G. PDB 1FQG traps the acylated reaction intermediate; it is not a wild-type apo design target.
Non-interactive alternative: The target-specification table below describes the relevant chain, catalytic site, and pocket residues. You can also open the 1FQG structure record or download its PDB coordinates. Manipulating the 3D viewer is optional.
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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 |
| Entry caveat | E166N mutant with covalently bound penicillin G; restore the wild-type Glu166 state or choose a verified wild-type structure before a final design campaign |
| 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 |
| Wild-type catalytic residues | S70 (nucleophile), K73 (general base), S130 (proton shuttle), E166 (deacylation), K234 (substrate positioning); position 166 is Asn in 1FQG |
| Ω-loop (substrate specificity) | residues 161–179 — these rim the active-site cleft |
| Provisional rim steering set | A104,A105,A168,A171,A239,A240 (E104, Y105, E168, E171, E239, R240), selected from comparatively exposed positions around the cleft |
The contact list identifies positions lining the small-molecule pocket, but many are too buried to steer a protein binder. The provisional course set instead samples comparatively exposed parts of the 104–105, Ω, and 239–240 rim regions. It is geometry-derived, not an energetic-hotspot claim, and must be rechecked after restoring wild-type position 166 or choosing another structure.
Strategy Tips
- Download PDB
1FQG. - Prepare the target deliberately: Keep Chain A and remove water and bound penicillin (
PNM). If the design is meant to target wild-type TEM-1, restore N166 to Glu with a documented structure-preparation protocol and inspect/relax the local geometry—or switch to a verified wild-type structure and re-map every steering residue. Do not silently treat 1FQG as wild type. - Choose a strategy:
- Active-site occlusion: after target preparation, begin with the provisional rim set
A104,A105,A168,A171,A239,A240and confirm solvent exposure visually or by SASA before generation. - 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: after target preparation, begin with the provisional rim set
- 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.