title: Structural Insights into Recognition of Hydrolyzed Carbapenems and Inhibitors by Subclass B3 Metallo-β-Lactamase SMB-1.
abstract: Metallo-β-lactamases (MBLs) confer resistance to carbapenems, and their increasing global prevalence is a growing clinical concern. To elucidate the mechanisms by which these enzymes recognize and hydrolyze carbapenems, we solved 1.4 to 1.6 Å crystal structures of SMB-1 (Serratia metallo-β-lactamase 1), a subclass B3 MBL, bound to hydrolyzed carbapenems (doripenem, meropenem, and imipenem). In these structures, SMB-1 interacts mainly with the carbapenem core structure via elements in the active site, including a zinc ion (Zn-2), Q157[113] (where the position in the SMB-1 sequence is in brackets after the BBL number), S221[175], and T223[177]. There is less contact with the carbapenem R2 side chains, strongly indicating that SMB-1 primarily recognizes the carbapenem core structure. This is the first report describing how a subclass B3 MBL recognizes carbapenems. We also solved the crystal structure of SMB-1 in complex with the approved drugs captopril, an inhibitor of the angiotensin-converting enzyme, and 2-mercaptoethanesulfonate, a chemoprotectant. These drugs are inhibitors of SMB-1 with Ki values of 8.9 and 184 μM, respectively. Like carbapenems, these inhibitors interact with Q157[113] and T223[177] and their thiol groups coordinate the zinc ions in the active site. Taken together, the data indicate that Q157[113], S221[175], T223[177], and the two zinc ions in the active site are key targets in the design of SMB-1 inhibitors with enhanced affinity. The structural data provide a solid foundation for the development of effective inhibitors that would overcome the carbapenem resistance of MBL-producing multidrug-resistant microbes.
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Aichi, Japan wachino@med.nagoya-u.ac.jp.
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Wachino
authors.affiliation: Environmental Safety Center, Kumamoto University, Chuo-ku, Kumamoto, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yamaguchi
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashi-Murayama, Tokyo, Japan.
authors.forename: Shigetarou
authors.initials: S
authors.lastname: Mori
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Aichi, Japan.
authors.forename: Wanchun
authors.initials: W
authors.lastname: Jin
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Aichi, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kimura
authors.affiliation: College of Pharmacy, Kinjo Gakuin University, Moriyama-ku, Nagoya, Aichi, Japan.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Kurosaki
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, Showa-ku, Nagoya, Aichi, Japan.
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Arakawa
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000737:chemistry; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002216:Captopril / Q000737:chemistry; D015780:Carbapenems / Q000737:chemistry*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D000077726:Doripenem; D015378:Imipenem / Q000737:chemistry; D000077731:Meropenem; D015080:Mesna / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012706:Serratia marcescens / Q000201:enzymology; D013845:Thienamycins / Q000737:chemistry; D001618:beta-Lactamases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000900:Anti-Bacterial Agents; D015780:Carbapenems; D013845:Thienamycins; D015378:Imipenem; D002216:Captopril; D000077726:Doripenem; D001618:beta-Lactamases; D000077731:Meropenem; D015080:Mesna