Title: Structural Insights into the Mechanism of Carbapenemase Activity of the OXA-48 β-Lactamase

Abstract

Carbapenem-hydrolyzing class D carbapenemases (CHDLs) are enzymes that produce resistance to the last-resort carbapenem antibiotics, severely compromising the available therapeutic options for the treatment of life-threatening infections. A broad variety of CHDLs, including OXA-23, OXA-24/40, and OXA-58, circulate in Acinetobacter baumannii, while the OXA-48 CHDL is predominant in Enterobacteriaceae. Extensive structural studies of A. baumannii enzymes have provided important information regarding their interactions with carbapenems and significantly contributed to the understanding of the mechanism of their carbapenemase activity. However, the interactions between carbapenems and OXA-48 have not yet been elucidated. We determined the X-ray crystal structures of the acyl-enzyme complexes of OXA-48 with four carbapenems, imipenem, meropenem, ertapenem, and doripenem, and compared them with those of known carbapenem complexes of A. baumannii CHDLs. In the A. baumannii enzymes, acylation by carbapenems triggers significant displacement of one of two conserved hydrophobic surface residues, resulting in the formation of a channel for entry of the deacylating water into the active site. We show that such a channel preexists in apo–OXA-48 and that only minor displacement of the conserved hydrophobic surface residues occurs upon the formation of OXA-48 acyl-enzyme intermediates. We also demonstrate that the extensive hydrophobic interactions that occur between a conservedmore » hydrophobic bridge of the A. baumannii CHDLs and the carbapenem tails are lost in OXA-48 in the absence of an equivalent bridge structure. In conclusion, these data highlight significant differences between the interactions of carbapenems with OXA-48 and those with A. baumannii enzymes and provide important insights into the mechanism of carbapenemase activity of the major Enterobacteriaceae CHDL, OXA-48.« less

Authors:

Smith, Clyde A. ^[1]; Stewart, Nichole K. ^[2]; Toth, Marta ^[2]; Vakulenko, Sergei B. ^[2]

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+ Show Author Affiliations

1. Stanford Univ., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource
2. Univ. of Notre Dame, Notre Dame, IN (United States). Dept. of Chemistry and Biochemistry

Publication Date:

2019-09-23

Research Org.:

SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1576949

Grant/Contract Number:  

AC02-76SF00515; R01AI114668; P41GM103393

Resource Type:

Accepted Manuscript

Journal Name:

Antimicrobial Agents and Chemotherapy

Additional Journal Information:

Journal Volume: 63; Journal Issue: 10; Journal ID: ISSN 0066-4804

Publisher:

American Society for Microbiology

Country of Publication:

United States

Language:

English

Subject:

60 APPLIED LIFE SCIENCES; antibiotic resistance; drug resistance mechanisms