1c3b
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(New page: 200px<br /><applet load="1c3b" size="450" color="white" frame="true" align="right" spinBox="true" caption="1c3b, resolution 2.25Å" /> '''AMPC BETA-LACTAMASE ...)
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Revision as of 10:00, 20 November 2007
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AMPC BETA-LACTAMASE FROM E. COLI COMPLEXED WITH INHIBITOR, BENZO(B)THIOPHENE-2-BORONIC ACID (BZB)
Overview
Beta-lactamases are the major resistance mechanism to beta-lactam, antibiotics and pose a growing threat to public health. Recently, bacteria, have become resistant to beta-lactamase inhibitors, making this problem, pressing. In an effort to overcome this resistance, non-beta-lactam, inhibitors of beta-lactamases were investigated for complementarity to the, structure of AmpC beta-lactamase from Escherichia coli. This led to the, discovery of an inhibitor, benzo(b)thiophene-2-boronic acid (BZBTH2B), which inhibited AmpC with a Ki of 27 nM. This inhibitor is chemically, dissimilar to beta-lactams, raising the question of what specific, interactions are responsible for its activity. To answer this question, the X-ray crystallographic structure of BZBTH2B in complex with AmpC was, determined to 2.25 A resolution. The structure reveals several unexpected, interactions. The inhibitor appears to complement the conserved, R1-amide, binding region of AmpC, despite lacking an amide group. Interactions, between one of the boronic acid oxygen atoms, Tyr150, and an ordered water, molecule suggest a mechanism for acid/base catalysis and a direction for, hydrolytic attack in the enzyme catalyzed reaction. To investigate how a, non-beta-lactam inhibitor would perform against resistant bacteria, BZBTH2B was tested in antimicrobial assays. BZBTH2B significantly, potentiated the activity of a third-generation cephalosporin against, AmpC-producing resistant bacteria. This inhibitor was unaffected by two, common resistance mechanisms that often arise against beta-lactams in, conjunction with beta-lactamases. Porin channel mutations did not decrease, the efficacy of BZBTH2B against cells expressing AmpC. Also, this, inhibitor did not induce expression of AmpC, a problem with many, beta-lactams. The structure of the BZBTH2B/AmpC complex provides a, starting point for the structure-based elaboration of this class of, non-beta-lactam inhibitors.
About this Structure
1C3B is a Single protein structure of sequence from Escherichia coli with BZB as ligand. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.
Reference
The complexed structure and antimicrobial activity of a non-beta-lactam inhibitor of AmpC beta-lactamase., Powers RA, Blazquez J, Weston GS, Morosini MI, Baquero F, Shoichet BK, Protein Sci. 1999 Nov;8(11):2330-7. PMID:10595535
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