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The complexed structure and antimicrobial activity of a non‐β‐lactam inhibitor of AmpC β‐lactamase
Author(s) -
Powers Rachel A.,
Blázquez Jesús,
Weston G. Scott,
Shoichet Brian K.,
Morosini MaríaIsabel,
Baquero Fernando
Publication year - 1999
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.8.11.2330
Subject(s) - beta lactamase inhibitors , antimicrobial , chemistry , porin , active site , boronic acid , antibiotic resistance , escherichia coli , stereochemistry , enzyme , biochemistry , microbiology and biotechnology , biology , antibiotics , bacterial outer membrane , combinatorial chemistry , gene
β‐Lactamases are the major resistance mechanism to β‐lactam antibiotics and pose a growing threat to public health. Recently, bacteria have become resistant to β‐lactamase inhibitors, making this problem pressing. In an effort to overcome this resistance, non‐β‐lactam inhibitors of β‐lactamases were investigated for complementarity to the structure of AmpC β‐lactamase from Escherichia coli . This led to the discovery of an inhibitor, benzo (b)thiophene‐2‐boronic acid (BZBTH2B), which inhibited AmpC with a K i t of 27 nM. This inhibitor is chemically dissimilar to β‐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 Å 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‐β‐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 β‐lactams in conjunction with β‐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 β‐lactams. The structure of the BZBTH2B/AmpC complex provides a starting point for the structure‐based elaboration of this class of non‐β‐lactam inhibitors.