Part:BBa_K3766012
AmpR
This part is AmpR, an E. coli gene coding for a β-lactamase enzyme. It is a derivative of the TEM-1 β-lactamase (Uniprot P62593) with two mutations V82I and V182A. In addition, compared to the sequence found in pSB1A2 from which it was derived by PCR amplification, a synonymous mutation S240 (TCC->TCG) and a non synonymous mutation were detected L223I (CTT->ATT) that did not affect the capacity of this enzyme to confer resistance to ampicillin when expressed in Escherichia coli.
Usage and Biology
AmpR is a protein associated with the resistance mechanism against the large family of β-lactams, antibiotics which include the well known penicillin and ampicillin.
β-Lactamases act by hydrolysing the β-lactam ring (Figure 1), thus inactivating the antibiotic.
Figure 1. The mode of action of β-lactamases: hydrolysis of the β-lactam ring.
Fortunately, among all the subgroups of β-lactams (table 1), some have less affinity with the β-lactamase(s) and overcome this resistance. For example, in monobactams, Aztreonam is known to have a bactericidal effect even on bacteria carrying the AmpR gene [1]. We confirmed this experimentally by testing the resistance of the bacteria carrying AmpR to different β-lactam antibiotics (Figure 2).
| Table 1. β-lactam groups and sub-groups, classified based on their core ring structures. | ||||||||
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| penams | carbapenams | clavams | penems | carbapenems | cephems | carbacephems | oxacephems | monobactams |
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[File: T--Evry_Paris-Saclay--AmpR_Ampi-Azt-Cefo-Cepha-Meth.png|center]]
Figure 2. Pictures of E. coli NEB5ɑ cells carrying the AmpR resistance gene (this part) plated on different concentrations of β-lactam antibiotics.
References
[1] Cantu C, Huang W, Palzkill T. Selection and characterization of amino acid substitutions at residues 237-240 of TEM-1 beta-lactamase with altered substrate specificity for aztreonam and ceftazidime. The Journal of Biological Chemistry (1996) 271: 22538–22545.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000COMPATIBLE WITH RFC[1000]
| None |