Sandbox 123
From Proteopedia
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| - | MRSA becomes resistant to β-lactams by acquiring an alternative PBP, PBP2a, that is neither bound nor inhibited by β-lactams. Recently, two cephalosporins – ceftobiprole and ceftaroline – that have anti-MRSA activity have been developed. Ceftobiprole is able to inhibit PBP2a because additional chemical groups at the R2 position of the cephalosporin backbone are able to interact with additional amino acid residues in PBP2a; specifically <scene name='36/365380/Ser403/16'>Tyr446</scene> and <scene name='36/365380/4dki_cartoon/ | + | MRSA becomes resistant to β-lactams by acquiring an alternative PBP, PBP2a, that is neither bound nor inhibited by β-lactams. Recently, two cephalosporins – ceftobiprole and ceftaroline – that have anti-MRSA activity have been developed. Ceftobiprole is able to inhibit PBP2a because additional chemical groups at the R2 position of the cephalosporin backbone are able to interact with additional amino acid residues in PBP2a; specifically <scene name='36/365380/Ser403/16'>Tyr446</scene> and <scene name='36/365380/4dki_cartoon/17'>Met641</scene>. As a result of its tighter binding to PBP2a, ceftobiprole is able to more efficiently react with the serine active site residue and therefore inhibit the activity of PBP2a. |
Revision as of 18:06, 29 July 2013
Introduction
, also known as penicillin-binding proteins (PBP), catalyze the cross-linking of peptidoglycan polymers during bacterial cell wall synthesis. The natural transpeptidase substrate is the D-Ala-D-Ala peptidoglycan side chain terminus. β-lactam antibiotics, which include penicillins, cephalosporins and carbapenems,have been used to treat Staphylococcus aureus infections. The overuse and misuse of β-lactam antibiotics has led to strains of Staphylococcus aureus that are resistant to all β-lactams; so called MRSA strains. MRSA can be hospital- or community-acquired and are often the cause of significant morbidity and mortality.
β-Lactam antibiotics stop the production of the cell wall by targeting bacterial PBPs. The cell wall, which is composed of peptidoglycan and surrounds the cell membrane, is crucial for maintaining the structural integrity of the bacterium.
The cell wall is composed of rows of peptidoglycan cross-linked together with pentaglycine chains. Peptidoglycan consists of N-acetylmuramic Acid (NAM) and N-acetylglucosamine (NAG) polymers. The NAM residues have a five amino acid side chain that terminates with two D-Alanine (D-Ala) residues.
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