Structural insights into the substrate specificity of SP_0149, the substrate-binding protein of a methionine ABC transporter from Streptococcus pneumoniae
01 Jul 2019-Acta Crystallographica Section F-structural Biology and Crystallization Communications (International Union of Crystallography)-Vol. 75, Iss: 7, pp 520-528
TL;DR: The structure of the SP_0149-Met complex provides insights into the transport function of SP-0149 and its interactions with methionine, and opens up avenues for the rational design of inhibitors of SP_ 0149 through a structure-mediated approach.
Abstract: Successful pathogenesis is a cumulative effect of the virulence factors of a pathogen and its capability to efficiently utilize the available nutrients from the host. Streptococcus pneumoniae, a Gram-positive opportunistic pathogen, may either reside asymptomatically as a nasopharyngeal commensal inside the human host or cause lethal diseases, including pneumonia, meningitis and sepsis. S. pneumoniae is known to acquire methionine (Met) from its host through a Met importer. Here, the crystal structure of the substrate-binding protein (SBP; SP_0149) of an ABC importer with Met bound is reported at a resolution of 1.95 A. The three-dimensional structure of SBP shows that it is composed of two distinct domains, each consisting of a mixed β-sheet flanked by helices. The substrate, Met, is bound in the central part of the interface between the two domains. The overall structure of SP_0149 resembles those of SBPs from other reported bacterial Met and Gly-Met dipeptide transporters. However, a detailed analysis of these structures shows notable variations in the amino-acid composition of the substrate-binding pockets of the SP_0149–Met and GmpC–Gly-Met structures. In particular, SP_0149 harbors Thr212 and Tyr114, whereas the corresponding residues in GmpC are Gly and Val. This difference is likely to be the underlying basis for their differential substrate specificity. In summary, the structure of the SP_0149–Met complex provides insights into the transport function of SP_0149 and its interactions with methionine. It opens up avenues for the rational design of inhibitors of SP_0149 through a structure-mediated approach.
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TL;DR: The methods presented in the chapter have been applied to solve a large variety of problems, from inorganic molecules with 5 A unit cell to rotavirus of 700 A diameters crystallized in 700 × 1000 × 1400 A cell.
Abstract: Publisher Summary X-ray data can be collected with zero-, one-, and two-dimensional detectors, zero-dimensional (single counter) being the simplest and two-dimensional the most efficient in terms of measuring diffracted X-rays in all directions. To analyze the single-crystal diffraction data collected with these detectors, several computer programs have been developed. Two-dimensional detectors and related software are now predominantly used to measure and integrate diffraction from single crystals of biological macromolecules. Macromolecular crystallography is an iterative process. To monitor the progress, the HKL package provides two tools: (1) statistics, both weighted (χ2) and unweighted (R-merge), where the Bayesian reasoning and multicomponent error model helps obtain proper error estimates and (2) visualization of the process, which helps an operator to confirm that the process of data reduction, including the resulting statistics, is correct and allows the evaluation of the problems for which there are no good statistical criteria. Visualization also provides confidence that the point of diminishing returns in data collection and reduction has been reached. At that point, the effort should be directed to solving the structure. The methods presented in the chapter have been applied to solve a large variety of problems, from inorganic molecules with 5 A unit cell to rotavirus of 700 A diameters crystallized in 700 × 1000 × 1400 A cell.
31,667 citations
"Structural insights into the substr..." refers methods in this paper
...The best data set was indexed, integrated and scaled using HKL-2000 (Otwinowski & Minor, 1997)....
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TL;DR: CCP4mg is a project that aims to provide a general-purpose tool for structural biologists, providing tools for X-ray structure solution, structure comparison and analysis, and publication-quality graphics.
Abstract: CCP4mg is a project that aims to provide a general-purpose tool for structural biologists, providing tools for X-ray structure solution, structure comparison and analysis, and publication-quality graphics. The map-fitting tools are available as a stand-alone package, distributed as `Coot'.
27,505 citations
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...Amino acids specific to SP_0149 were incorporated/replaced in the polypeptide chain based on electron-density maps (2|Fo| |Fc| at 1 and |Fo| |Fc| at 3 contour levels) using the model-building program Coot (Emsley & Cowtan, 2004)....
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Abstract: The PROCHECK suite of programs provides a detailed check on the stereochemistry of a protein structure Its outputs comprise a number of plots in PostScript format and a comprehensive residue-by-residue listing These give an assessment of the overall quality of the structure as compared with well refined structures of the same resolution and also highlight regions that may need further investigation The PROCHECK programs are useful for assessing the quality not only of protein structures in the process of being solved but also of existing structures and of those being modelled on known structures
22,829 citations
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...The stereochemistry of each and every residue of the structure was checked using the PROCHECK (Laskowski et al., 1993)....
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TL;DR: A description is given of Phaser-2.1: software for phasing macromolecular crystal structures by molecular replacement and single-wavelength anomalous dispersion phasing.
Abstract: Phaser is a program for phasing macromolecular crystal structures by both molecular replacement and experimental phasing methods. The novel phasing algorithms implemented in Phaser have been developed using maximum likelihood and multivariate statistics. For molecular replacement, the new algorithms have proved to be significantly better than traditional methods in discriminating correct solutions from noise, and for single-wavelength anomalous dispersion experimental phasing, the new algorithms, which account for correlations between F+ and F−, give better phases (lower mean phase error with respect to the phases given by the refined structure) than those that use mean F and anomalous differences ΔF. One of the design concepts of Phaser was that it be capable of a high degree of automation. To this end, Phaser (written in C++) can be called directly from Python, although it can also be called using traditional CCP4 keyword-style input. Phaser is a platform for future development of improved phasing methods and their release, including source code, to the crystallographic community.
17,755 citations
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...F75, 520–528 Jha et al. Substrate specificity of SP_0149 521 Staphylococcus aureus (Williams et al., 2004; PDB entry 1p99) in Phaser (McCoy et al., 2007) from the CCP4 suite (Winn et al., 2011)....
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TL;DR: A set of simple and physically motivated criteria for secondary structure, programmed as a pattern‐recognition process of hydrogen‐bonded and geometrical features extracted from x‐ray coordinates is developed.
Abstract: For a successful analysis of the relation between amino acid sequence and protein structure, an unambiguous and physically meaningful definition of secondary structure is essential. We have developed a set of simple and physically motivated criteria for secondary structure, programmed as a pattern-recognition process of hydrogen-bonded and geometrical features extracted from x-ray coordinates. Cooperative secondary structure is recognized as repeats of the elementary hydrogen-bonding patterns “turn” and “bridge.” Repeating turns are “helices,” repeating bridges are “ladders,” connected ladders are “sheets.” Geometric structure is defined in terms of the concepts torsion and curvature of differential geometry. Local chain “chirality” is the torsional handedness of four consecutive Cα positions and is positive for right-handed helices and negative for ideal twisted β-sheets. Curved pieces are defined as “bends.” Solvent “exposure” is given as the number of water molecules in possible contact with a residue. The end result is a compilation of the primary structure, including SS bonds, secondary structure, and solvent exposure of 62 different globular proteins. The presentation is in linear form: strip graphs for an overall view and strip tables for the details of each of 10.925 residues. The dictionary is also available in computer-readable form for protein structure prediction work.
14,077 citations
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...The secondary-structural elements were assigned using DSSP (Kabsch & Sander, 1983)....
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