Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Electrostatic interactions play a key role in many aspects of protein engineering. Consequently, much effort has been put into the design of software for calculating electrostatic fields around macromolecules. We show that optimization of hydrogen bonding networks can improve both the results of pK(a) calculations and the results of electrostatic calculations performed by commonly used programs such as DelPhi. Further optimization can often be achieved by flipping the side chains of asparagine, histidine and glutamine around their chi2, chi2 and chi3 torsion angles, respectively, when this improves the local hydrogen bonding network. These optimizations are applied to some well characterized proteins: BPTI, hen egg white lysozyme and superoxide dismutase. A search for flipped residues in the PDB revealed that significant improvements in electrostatic calculations in or near the active site of enzymes can be expected for about one quarter of all enzymes in the PDB.
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PMID:Improving macromolecular electrostatics calculations. 1046 26

In order to address the recognition mechanism of the fragments of antibody variable regions, termed Fv, toward their target antigen, an x-ray crystal structure of an anti-hen egg white lysozyme antibody (HyHEL-10) Fv fragment complexed with its cognate antigen, hen egg white lysozyme (HEL), was solved at 2.3 A. The overall structure of the complex is similar to that reported in a previous article dealing with the Fab fragment-HEL complex (PDB ID code,). However, the areas of Fv covered by HEL upon complex formation increased by about 100 A(2) in comparison with the Fab-HEL complex, and two local structural differences were observed in the heavy chain of the variable region (VH). In addition, small but significant local structural changes were observed in the antigen, HEL. The x-ray data permitted the identification of two water molecules between the VH and HEL and six water molecules retained in the interface between the antigen and the light chain complementarity determining regions (CDRs) 2 and 3 (CDR-L2 and CDR-L3). These water molecules bridge the antigen-antibody interface through hydrogen bond formation in the VL-HEL interface. Eleven water molecules were found to complete the imperfect VH-VL interface, suggesting that solvent molecules mediate the stabilization of interaction between variable regions. These results suggest that the unfavorable effect of deletion of constant regions on the antigen-antibody interaction is compensated by an increase in favorable interactions, including structural changes in the antigen-antibody interface and solvent-mediated hydrogen bond formation upon complex formation, which may lead to a minimum decreased affinity of the antibody Fv fragment toward its antigen.
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PMID:Crystal structure of anti-Hen egg white lysozyme antibody (HyHEL-10) Fv-antigen complex. Local structural changes in the protein antigen and water-mediated interactions of Fv-antigen and light chain-heavy chain interfaces. 1048 2

AmpD is a bacterial amidase involved in the recycling of cell-wall fragments in Gram-negative bacteria. Inactivation of AmpD leads to derepression of beta-lactamase expression, presenting a major pathway for the acquisition of constitutive antibiotic resistance. Here, we report the NMR structure of AmpD from Citrobacter freundii (PDB accession code 1J3G). A deep substrate-binding pocket explains the observed specificity for low molecular mass substrates. The fold is related to that of bacteriophage T7 lysozyme. Both proteins bind zinc at a conserved site and require zinc for amidase activity, although the enzymatic mechanism seems to differ in detail. The structure-based sequence alignment identifies conserved features that are also conserved in the eukaryotic peptidoglycan recognition protein (PGRP) domains, including the zinc-coordination site in several of them. PGRP domains thus belong to the same fold family and, where zinc-binding residues are conserved, may have amidase activity. This hypothesis is supported by the observation that human serum N-acetylmuramyl-L-alanine amidase seems to be identical with a soluble form of human PGRP-L.
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PMID:NMR structure of Citrobacter freundii AmpD, comparison with bacteriophage T7 lysozyme and homology with PGRP domains. 1265 66

The crystal structure of the complex of the antibody Fab, HyHEL-5, with its antigen, hen egg-white lysozyme, has been refined at 2.65 A resolution to an R value of 0.196. The resulting model has significantly better stereochemistry than the previously reported model of the complex, PDB reference 2HFL, and sufficiently improved phases, permitting the reliable location of a number of water molecules. No major conformational differences are observed between this structure and that previously reported, although small differences occur throughout the complex. 82 water molecules have been assigned, of which three are in the antibody-antigen interface involved in a hydrogen-bonding network. Three other waters are trapped within the interface between V(H) and V(L) and a fourth water molecule is observed near the interface but buried below the lysozyme surface as observed in crystal structures of lysozyme alone.
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PMID:Refined structure of the monoclonal antibody HyHEL-5 with its antigen hen egg-white lysozyme. 1529 4

The structure of hexagonal turkey egg-white lysozyme (TEWL) has been determined and refined at 1.65 A resolution. The crystals were grown from a 150 mM potassium thiocyanate solution at pH 4.5 and belong to space group P6(1)22 with unit-cell dimensions a = b = 70.96, c = 83.01 A alpha = beta = 90, gamma = 120 degrees. The crystals were isomorphous with those of hexagonal pH 8.0 TEWL. The coordinates of PDB entry code 3LZ2 were therefore used as the initial model and subjected to rigid-body refinement, simulated annealing and least-squares refinement to a final residual of 0.20. The root-mean-square deviations from the ideal bond distances and angles were 0.016 A and 2.2 degrees, respectively. During the refinement, 86 water molecules and one thiocyanate ion were located in the structure. The thiocyanate ion lies close to the interface between two symmetry-related molecules. The S atom of the ion forms two direct intermolecular contacts with Argl4 and interacts indirectly via a network of water molecules to Arg5 of a symmetry-related molecule. The structure provides direct evidence for the mode of thiocyanate binding to arginine residues and suggests a possible mechanism for the efficiency of thiocyanate in crystallizing basic proteins.
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PMID:Structure of hexagonal turkey egg-white lysozyme at 1.65A resolution. 1529 95

The structure of turkey egg-white lysozyme (TEWL) has been refined from high-resolution X-ray powder diffraction data. The sample was rapidly obtained as a polycrystalline precipitate at high protein concentration using 0.5 M NaCl solvent pH 6 and was deposited in the PDB with code 1xft. The diffraction data were collected at room temperature. Molecular replacement was shown to give a suitable starting point for refinement, illustrating that powder data can be sufficient for this approach. Crystallographic models were then refined by combined Rietveld and stereochemical restraint analysis of the powder data (d(min) = 3.35 A), resulting in the extraction of reliable lattice parameters and the refinement of the molecular conformation at room temperature. The structure is hexagonal [space group P6(1)22, unit-cell parameters a = 71.0862 (3), c = 85.0276 (5) A] with 12 symmetry-related molecules in the unit cell, in agreement with previous studies. The results of our analysis are indicative of specific amino acids being disordered at this temperature. Upon cooling, a sudden drop in the lattice parameters at approximately 250 K is observed concurrently with the freezing of the mother liquor. The observation of severe peak broadening below this temperature indicates strain effects accompanying the freezing transition, which are found to be reversible. Finally, a correlation between the unit-cell parameters and the pH of the buffer solution is evident, in a similar manner to earlier observations on HEWL.
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PMID:Synchrotron X-ray powder diffraction study of hexagonal turkey egg-white lysozyme. 1580 97

In this work, we present a generalization of Zwanzig's protein unfolding analysis [Zwanzig, R., 1997. Two-state models of protein folding kinetics. Proc. Natl Acad. Sci. USA 94, 148-150; Zwanzig, R., 1995. Simple model of protein folding kinetics. Proc. Natl Acad. Sci. USA 92, 9801], in order to calculate the free energy change Delta(N)(D)F between the protein's native state N and its unfolded state D in a chemically induced denaturation. This Extended Zwanzig Model (EZM) is both based on an equilibrium statistical mechanics approach and the inclusion of experimental denaturation curves. It enables us to construct a suitable partition function Z and to derive an analytical formula for Delta(N)(D)F in terms of the number K of residues of the macromolecule, the average number nu of accessible states for each single amino acid and the concentration C(1/2) where the midpoint of the N<==>D transition occurs. The results of the EZM for proteins where chemical denaturation follows a sigmoidal-type profile, as it occurs for the case of the T70N human variant of lysozyme (PDB code: T70N) [Esposito, G., et al., 2003. J. Biol. Chem. 278, 25910-25918], can be splitted into two lines. First, EZM shows that for sigmoidal denaturation profiles, the internal degrees of freedom of the chain play an outstanding role in the stability of the native state. On the other hand, that under certain conditions DeltaF can be written as a quadratic polynomial on concentration C(1/2), i.e., DeltaF approximately aC(1/2)(2)+bC(1/2)+c, where a,b,c are constant coefficients directly linked to protein's size K and the averaged number of non-native conformations nu. Such functional form for DeltaF has been widely known to fit experimental measures in chemically induced protein denaturation [Yagi, M., et al., 2003. J. Biol. Chem. 278, 47009-47015; Asgeirsson, B., Guojonsdottir, K., 2006. Biochim. Biophys. Acta 1764, 190-198; Sharma, S., et al., 2006. Protein Pept. Lett. 13(4), 323-329; Salem, M., et al., 2006. Biochim. Biophys. Acta 1764(5), 903-912] so EZM can shed some light into the physical meaning of the experimental values for the a,b,c coefficients.
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PMID:Protein's native state stability in a chemically induced denaturation mechanism. 1730 31

Langevin mode theory and the coarse-grained elastic network model (ENM) for proteins are combined to yield the Langevin network model (LNM). Hydrodynamic radii of 6 A were assigned to each alpha-carbon on the basis of matching experimental translational and rotational diffusion constants of lysozyme, myoglobin, and hemoglobin with those calculated using a rigid body bead model with hydrodynamic interactions described by the Rotne-Prager tensor. LNM analysis of myosin II indicates that all ENM-like modes are overdamped at water viscosities. The low-frequency LNM modes in the pre-power stroke structure (PDB code: 1VOM) are substantially less mixed than the corresponding modes of the post-power stroke structure (1Q5G). Results from a four-bead model of the myosin "lever arm" indicate that coupling between modes increases as the array departs from linearity and are consistent with the results for 1VOM and 1Q5G. The decay times for all overdamped Langevin modes are shorter than the calculated rotational tumbling times found for lysozyme and myosin.
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PMID:Langevin network model of myosin. 1831 63

The C-terminus of gp36 of bacteriophage varphiKMV (KMV36C) functions as a particle-associated muramidase, presumably as part of the injection needle of the phiKMV genome during infection. Crystals of KMV36C were obtained by hanging-drop vapour diffusion and diffracted to a resolution of 1.6 A. The crystals belong to the cubic space group P432, with unit-cell parameters a = b = c = 102.52 A. KMV36C shows 30% sequence identity to T4 lysozyme (PDB code 1l56).
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PMID:Structural analysis of bacteriophage-encoded peptidoglycan hydrolase domain KMV36C: crystallization and preliminary X-ray diffraction. 1839 22

The peptidoglycan glycosyltransferase (GT) module of class A penicillin-binding proteins (PBPs) and monofunctional GTs catalyze glycan chain elongation of the bacterial cell wall. These enzymes belong to the GT51 family, are characterized by five conserved motifs, and have some fold similarity with the phage lambda lysozyme. In this work, we have systematically modified all the conserved amino acid residues of the GT module of Escherichia coli class A PBP1b by site-directed mutagenesis and determined their importance for the in vivo and in vitro activity and the thermostability of the protein. To get an insight into the GT active site of this paradigm enzyme, a model of PBP1b GT domain was constructed based on the available crystal structures (PDB codes 2OLV and 2OLU). The data show that in addition to the essential glutamate residues Glu233 of motif 1 and Glu290 of motif 3, the residues Phe237 and His240 of motif 1 and Gly264, Thr267, Gln271, and Lys274 of motif 2, all located in the catalytic cavity of the GT domain, are essential for the in vitro enzymatic activity of the PBP1b and for its in vivo functioning. Thus, the first three conserved motifs contain most of the residues that are required for the GT activity of the PBP1b. The residues Asp234, Phe237, His240, Thr267, and Gln271 are proposed to maintain the structure of the active site and the positioning of the catalytic Glu233.
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PMID:Importance of the conserved residues in the peptidoglycan glycosyltransferase module of the class A penicillin-binding protein 1b of Escherichia coli. 1870 63


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