The ligands and the electron denseness maps, including omit maps, can be inspected using an interactive figure created with Molstack (http://molstack.bioreproducibility.org/project/view/FU0iFwAkG0vsoOtUDZd5/). We reprocessed the original X-ray diffraction data (https://proteindiffraction.org/project/apc105101_4HKY/) in the anomalous mode using corrections for radiation decay and anisotropic diffraction, built a missing fragment of the protein backbone (residues 31C40 of chain A), added two polyethylene glycol molecules, and refined anisotropic temperature factors for the Cd2+ ions. genetic elements, which often include additional resistance genes, making the microbiological scenario particularly alarming. There is an urgent need to develop MBL inhibitors in order to save our antibiotic armory. A number of such attempts have been carried out, most notably using the 3D constructions of various MBLs as drug-design focuses on. Structure-guided drug finding depends on the quality of the constructions that are collected in the Protein Data Standard bank (PDB) and on the regularity of the information in dedicated -lactamase databases. We carried out a careful review of the crystal constructions of class B -lactamases, concluding that the quality of these constructions varies widely, especially in the areas where small molecules interact with the macromolecules. In a number of good examples the interpretation of the bound ligands (e.g., inhibitors, substrate/product analogs) is definitely doubtful and even incorrect, and it appears that in some cases the modeling of ligands was not supported by electron denseness. For ten MBL constructions, alternate interpretations of the original diffraction data could be proposed and the new models have been deposited in the PDB. In four instances, these models, prepared jointly with the authors of the original depositions, superseded the previous deposits. This review emphasizes the importance of critical assessment of structural models describing PRKD1 key drug design focuses on at the level of the uncooked experimental data. Since the constructions reviewed here are the basis for ongoing design of fresh MBL inhibitors, it is important to identify and right the problems with ambiguous crystallographic interpretations, therefore enhancing reproducibility with this highly medically relevant area. with and without problematic ligands; and analysis of ligand relationships, such as H-bond distances, vehicle der Waals contacts, etc. The very isolated instances of structure fabrication (discussed in (Wlodawer et al., 2013)) can be disregarded with this context, as they have been rapidly recognized Epacadostat (INCB024360) and eliminated, leading in fact to the development of much improved tools for structure validation and error detection (Go through et al., 2011). More long-term harm is done by structural models deposited in the PDB that at face value do not raise red flags for the unsuspecting consumers (not necessarily familiar with structural biology), but on closer scrutiny demonstrate a Epacadostat (INCB024360) number of problems. The most severe problems are related to modeling ligands without the support of electron denseness (Pozharski et al., 2013; Wlodawer et al., 2017). For example, in a recent paper (Shabalin et al., 2015) we showed Epacadostat (INCB024360) that some protein complexes of cisplatin and carboplatin deposited in the PDB experienced troubling interpretational problems with modeling of the metal-coordination ligands. In another study, no experimental evidence could be found for the presence of ligands in a number of protein complexes, including antibody complexes (Wlodawer et al., 2017). In some cases, the constructions could be significantly corrected (and re-deposited) and given an alternative interpretation, or at least the original interpretation had to be put in severe doubt. In the present review, we have critically assessed the PDB models of metallo–lactamases (MBLs), a group of enzymes that are of high medical relevance. Metallo–lactamases are significantly contributing to the problem of antibiotic resistance, which has currently become one of the major health concerns (Davies and Davies, 2010; Frre et al., 2016; Mojica et al., 2016; Walsh et al., 2005; World Health Corporation, 2017). MBLs are broad-spectrum hydrolases, capable of breaking down almost all -lactam antibiotics, including carbapenems, which are considered the drugs of last resort (McKenna, 2013). Only monobactams are not hydrolyzed by MBLs. Fig. 1 shows a few examples of common -lactams. The most straightforward approach to combating MBL-related antibiotic resistance would be to develop efficient inhibitors with as wide a spectrum as you can. Such inhibitors, used in combination with the existing -lactam antibiotics, would save them for long term use. Toward this end, 235 MBL constructions (as of December 4, 2017) have been determined in different laboratories and deposited in the PDB. In addition, references to the people models, their classification, characterization, as well as literature sources, are being collected in a dedicated -Lactamase Database (www.bldb.eu(Naas et al., 2017)). Open in a separate window Number 1. (A) Some of the common -lactam antibiotics demonstrated with systematic numbering of the -lactam part and the fused ring. Ampicillin belongs to the penicillin class of -lactams, cephalexin and cefuroxime are cephalosporins, while meropenem is an example of a carbapenem. (B) The hydrolysis reaction scheme, demonstrated for any penicillin core example. In the case of unsaturated fused.