1C3B

AMPC BETA-LACTAMASE FROM E. COLI COMPLEXED WITH INHIBITOR, BENZO(B)THIOPHENE-2-BORONIC ACID (BZB)

Summary for 1C3B

• Entry DOI: 10.2210/pdb1c3b/pdb
• Related: 2BLS 3BLS
• Descriptor: CEPHALOSPORINASE, BENZO[B]THIOPHENE-2-BORONIC ACID (3 entities in total)
• Functional Keywords: cephalosporinase, beta-lactamase, serine hydrolase, hydrolase
• Biological source: Escherichia coli
• Cellular location: Periplasm: P00811
• Total number of polymer chains: 2
• Total formula weight: 79531.88

Authors

Powers, R.A.,Blazquez, J.,Weston, G.S.,Morosini, M.I.,Baquero, F.,Shoichet, B.K. (deposition date: 1999-07-27, release date: 1999-11-24, Last modification date: 2024-11-13)

Primary citation

Powers, R.A.,Blazquez, J.,Weston, G.S.,Morosini, M.I.,Baquero, F.,Shoichet, B.K.
The complexed structure and antimicrobial activity of a non-beta-lactam inhibitor of AmpC beta-lactamase.
Protein Sci., 8:2330-2337, 1999

PubMed Abstract: 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.

PubMed: 10595535

Experimental method

X-RAY DIFFRACTION (2.25 Å)