title: Structure-kinetic relationship of carbapenem antibacterials permeating through E. coli OmpC porin.
abstract: The emergence of Gram-negative "superbugs" exhibiting resistance to known antibacterials poses a major public health concern. Low molecular weight Gram-negative antibacterials are believed to penetrate the outer bacterial membrane (OM) through porin channels. Therefore, intracellular exposure needed to drive antibacterial target occupancy should depend critically on the translocation rates through these proteins and avoidance of efflux pumps. We used electrophysiology to study the structure-translocation kinetics relationships of a set of carbapenem antibacterials through purified porin OmpC reconstituted in phospholipid bilayers. We also studied the relative susceptibility of OmpC+ and OmpC- E. coli to these compounds as an orthogonal test of translocation. Carbapenems exhibit good efficacy in OmpC-expressing E. coli cells compared with other known antibacterials. Ertapenem, which contains an additional acidic group compared to other analogs, exhibits the fastest entry into OmpC (k(on) ≈ 2 × 10(4) M(-1) s(-1)). Zwitterionic compounds with highly polar groups attached to the penem-2 ring, including panipenem, imipenem and doripenem exhibit faster k(on) (>10(4) M(-1) s(-1)), while meropenem and biapenem with fewer exposed polar groups exhibit slower k(on) (∼5 × 10(3) M(-1) s(-1)). Tebipenem pivoxil and razupenem exhibit ∼13-fold slower k(on) (∼1.5 × 10(3) M(-1) s(-1)) than ertapenem. Overall, our results suggest that (a) OmpC serves as an important route of entry of these antibacterials into E. coli cells; and (b) that the structure-kinetic relationships of carbapenem translocation are governed by H-bond acceptor/donor composition (in accordance with our previous findings that the enthalpic cost of transferring water from the constriction zone to bulk solvent increases in the presence of exposed nonpolar groups).
authors.affiliation: Center for Proteomic Chemistry, Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, 02139.
authors.forename: Que-Tien
authors.initials: QT
authors.lastname: Tran
authors.forename: Robert A
authors.initials: RA
authors.lastname: Pearlstein
authors.forename: Sarah
authors.initials: S
authors.lastname: Williams
authors.forename: John
authors.initials: J
authors.lastname: Reilly
authors.forename: Thomas
authors.initials: T
authors.lastname: Krucker
authors.forename: Gül
authors.initials: G
authors.lastname: Erdemli
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D015780:Carbapenems / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008051:Lipid Bilayers; D008826:Microbial Sensitivity Tests; D010743:Phospholipids / Q000378:metabolism; D018272:Porins / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D015780:Carbapenems; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; C113724:OmpC protein; D010743:Phospholipids; D018272:Porins
keywords: antibiotics; drug transport; electrophysiology; gram-negative bacteria; membrane proteins; microbiology; translocation kinetics