Sandbox 1666
From Proteopedia
Contents |
CTX-M Beta-Lactamase
CTX-M Beta Lactamase is a class a enzyme. This enzyme creates drug resistance to ampicillin and cefotaxime through a two step process: deacylation and acylation.
Function of Protein
CTX-M Beta-Lactamase is an enzyme that is produced in bacteria, more specifically E. coli. CTX-M Beta-Lactamase is made to inhibit Beta-Lactam. Beta-Lactam binds with ampicillin and cefotaxime, which are both made to fight bacterial infections. It attacks the lactam ring that are in both of these structures, which causes deacylation to occur. is the overall structure of CTX-M Beta-Lactamase.
Known substrates of this protein are ampicillin and cefotaxime. These are key determinants of resistance to antibiotics. This also determines what drugs are susceptible of bacteria that harbor the enzymes.
Biological Relevance and Broader Implications
Since Beta-Lactam antibiotics are used very often in antimicrobial therapy to treat bacterial infections, bacterial resistance often ocurrs. This enzyme, CTX-M Beta-Lactamase, inhibits the drug's function by breaking apart the lactam ring, making it harder to treat. This is a problem because if we can understand it better, we can change the way we treat to fight off the bacteria better.
There have been several inhibitor-resistant variants that mutations have risen from. More specifically one of them being K23YR. This mutation causes a 1500-fold decrease in the cefotaxime and a 5-fold increase in the Kcat for ampicillin. This makes it become a good penicillinase, but a poor cephalosporinase due to slow acylation. The mutation of this will lead to the enzyme being inactivated, making the drug resistance not work efficiently.
The research of this protein is very significant because it has a direct clinical application.
Important Amino Acids
An important ligand of this protein is , which is the only ligand in this protein. GOL helps with stability of this protein. The consists of the amino acids Ser70 (green), Ser130 (blue), and Lys73 (pink). Ser70 interacts with the oxygen on the ampicillin, and it is also cross-linked with clavulanic acid. Ser130 is also cross-linked with clavulanic acid and interacts with the ligand through hydrogen bonds. Lys73 interacts with the ligand through hydrogen bonds used to lower the pka value of the hydroxyl group. Lys234 also plays an important role in the proton transfer during the catalysis of the antibiotics. An active site residue of this protein that causes deacylation to occur is Glu166. This residue activates a catalytic water molecule.
Structural highlights
This protein has eight chains. Each chain has eleven separate and nine separate . Some of the chains bind to GOL to help with stability. Within each chain, there are two of the catalytic amino acid within helix three. The last catalytic amino acid is located in helix seven. Both of these helices form important interactions with the ligands because of those catalytic amino acids.
The tertiary structure of the protein mainly upheld by hydrogen bonds and other noncovalent bonds while the quaternary structure has multiple chains.
Other Important Features
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