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Mechanisms of proton relay and product release by Class A ?-lactamase at ultrahigh resolution.

ABSTRACT: The ?-lactam antibiotics inhibit penicillin-binding proteins (PBPs) by forming a stable, covalent, acyl-enzyme complex. During the evolution from PBPs to Class A ?-lactamases, the ?-lactamases acquired Glu166 to activate a catalytic water and cleave the acyl-enzyme bond. Here we present three product complex crystal structures of CTX-M-14 Class A ?-lactamase with a ruthenocene-conjugated penicillin-a 0.85 Å resolution structure of E166A mutant complexed with the penilloate product, a 1.30 Å resolution complex structure of the same mutant with the penicilloate product, and a 1.18 Å resolution complex structure of S70G mutant with a penicilloate product epimer-shedding light on the catalytic mechanisms and product inhibition of PBPs and Class A ?-lactamases. The E166A-penilloate complex captured the hydrogen bonding network following the protonation of the leaving group and, for the first time, unambiguously show that the ring nitrogen donates a proton to Ser130, which in turn donates a proton to Lys73. These observations indicate that in the absence of Glu166, the equivalent lysine would be neutral in PBPs and therefore capable of serving as the general base to activate the catalytic serine. Together with previous results, this structure suggests a common proton relay network shared by Class A ?-lactamases and PBPs, from the catalytic serine to the lysine, and ultimately to the ring nitrogen. Additionally, the E166A-penicilloate complex reveals previously unseen conformational changes of key catalytic residues during the release of the product, and is the first structure to capture the hydrolyzed product in the presence of an unmutated catalytic serine. DATABASE:Structural data are available in the PDB database under the accession numbers 5TOP, 5TOY, and 5VLE.

SUBMITTER: Lewandowski EM

PROVIDER: S-EPMC5760336 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Mechanisms of proton relay and product release by Class A β-lactamase at ultrahigh resolution.

Lewandowski Eric M EM Lethbridge Kathryn G KG Sanishvili Ruslan R Skiba Joanna J Kowalski Konrad K Chen Yu Y

The FEBS journal 20171120 1

The β-lactam antibiotics inhibit penicillin-binding proteins (PBPs) by forming a stable, covalent, acyl-enzyme complex. During the evolution from PBPs to Class A β-lactamases, the β-lactamases acquired Glu166 to activate a catalytic water and cleave the acyl-enzyme bond. Here we present three product complex crystal structures of CTX-M-14 Class A β-lactamase with a ruthenocene-conjugated penicillin-a 0.85 Å resolution structure of E166A mutant complexed with the penilloate product, a 1.30 Å reso ...[more]

PMID: 29095570

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Project description:BACKGROUND & AIMS:Recognition of rumination and supragastric belching is often delayed as symptoms may be mistakenly attributed to gastroesophageal reflux disease. However, distinct from gastroesophageal reflux disease, rumination and supragastric belching are more responsive to behavioral interventions than to acid-suppressive and antireflux therapies. Postprandial high-resolution impedance manometry (PP-HRIM) is an efficient method to identify rumination and belches. We investigated the distribution of postprandial profiles determined by PP-HRIM, and identified patient features associated with postprandial profiles among patients with nonresponse to proton pump inhibitors (PPIs). METHODS:We performed a retrospective analysis of PP-HRIM studies performed on 94 adults (mean age, 50.6 y; 62% female) evaluated for PPI nonresponsiveness at an esophageal referral center, from January 2010 through May 2016. Following a standard esophageal manometry protocol, patients ingested a solid refluxogenic test meal (identified by patients as one that induces symptoms) with postprandial monitoring up to 90 minutes (median, 50 min). Patients were assigned to 1 of 4 postprandial profiles: normal; reflux only (>6 transient lower esophageal sphincter relaxations (TLESRs)/h); supragastric belch (>2 supragastric belches/h), with or without TLESR; or rumination (?1 rumination episode/h) with or without TLESR and supragastric belching. The primary outcome was postprandial profile. RESULTS:Of the study participants, 24% had a normal postprandial profile, 14% had a reflux-only profile, 42% had a supragastric belch profile, and 20% had a rumination profile. In multinomial regression analysis, the rumination group most frequently presented with regurgitation, the supragastric belch and rumination groups were younger in age, and the reflux-only group had a lower esophagogastric junction contractile integral. The number of weakly acidic reflux events measured by impedance-pH monitoring in patients receiving PPI therapy was significantly associated with frequency of rumination episodes and supragastric belches. CONCLUSIONS:In a retrospective analysis of 94 nonresponders to PPI therapy evaluated by PP-HRIM, we detected an abnormal postprandial pattern in 76% of cases: 42% of these were characterized as supragastric belching, 20% as rumination, and 14% as reflux only. Age, esophagogastric junction contractility, impedance-pH profiles, and symptom presentation differed significantly among groups. PP-HRIM can be used in the clinic to evaluate mechanisms of PPI nonresponse.

Dataset Information

Mechanisms of proton relay and product release by Class A ?-lactamase at ultrahigh resolution.

Publications

Mechanisms of proton relay and product release by Class A β-lactamase at ultrahigh resolution.

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