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)

Monocytes and tissue macrophages play important roles in host defense against virus infections and, in the case of human cytomegalovirus (HCMV) and HIV, may also be the reservoir for latent disease. Because these cells can also rapidly respond to most infections by secretion of inflammatory mediators, we were interested in determining if HCMV infection could have a direct activating effect on macrophage cytokine production. To do this, we primarily investigated the influence of HCMV infection on IL-1 beta-mRNA expression in peripheral blood monocytes and the promyelocytic cell line, ML-3 as well as the inflammatory response genes TNF-alpha, MAD-9, MAD-6, and MAD-2 in the promyelocytic ML-3 cell line. Exposure of ML-3 cells to the virus prior to induction of differentiation had little influence on mediator gene expression. However, induction of the macrophage phenotype by pretreatment of ML-3 cells with the phorbol ester, PMA, followed by HCMV challenge, resulted in a greatly extended period of expression of IL-1 beta, TNF-alpha, MAD-9, and CSF-1 but not MAD-6 and MAD-2. Constitutively expressed genes such as lysozyme and actin were not similarly modulated. Both RNA dot-blot and in situ hybridization studies demonstrated that infection of human peripheral blood monocytes with HCMV leads to sustained expression of IL-1 beta mRNA for up to 96 h, which contrasted markedly with mock-infected or LPS-stimulated monocytes. Flow cytometric analysis of the intracellular levels of IL-1 beta protein in ML-3 cells indicated that not only was there more protein produced in infected cells, but that the majority of the cells had responded. Enhanced levels of the intracellular form of IL-1 beta in monocytes was confirmed by Western blot analysis. Cotransfection experiments were performed using IL-1 beta-CAT chimeric plasmids together with plasmids encoding HCMV-immediate-early gene region products. Transactivation of the IL-1 beta gene by region 2 of the immediate-early gene was observed in ML-3 cells that had been induced to differentiate prior to transfection. No stimulation of IL-1 beta promoter activity was observed in ML-3 cells that were undifferentiated prior to transfection. In summary, HCMV infection, although not leading to productive infection, nonetheless may contribute to the pathology of the infection through enhancement of monocyte inflammatory mediator gene expression with subsequent stimulation of protein synthesis.
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PMID:Cytomegalovirus infection stimulates expression of monocyte-associated mediator genes. 255 12

A mutant of Escherichia coli has been found to have an increased sensitivity to actinomycin D and to sodium deoxycholate and an unusual morphology which accompanies an abnormality in cellular division. All of these characteristics are suppressed when the strain is grown in the presence of d-alanine. This strain, called MAD-1, for murein altered division mutant, exhibits its pleiotropic phenotype only when certain carbon compounds are used as energy sources in minimal medium. Nonpermissive carbon sources, which elicit the disturbed phenotype, include glucose, mannitol, fructose, maltose, and lactose; permissive carbon sources include galactose, glycerol, lactate, and succinate. The mutant is able to transport nonpermissive carbon compounds; 3 mM 3',5'-cyclic adenosine monophosphate included in the medium does not alter the phenotype seen with growth on glucose. Deoxyribonucleic acid and protein synthesis are normal with respect to cellular mass increase. d-Alanine specifically suppresses the pleiotropic phenotype at a concentration six times lower than l-alanine, the only other compound found to be effective. There is no abnormality in the K(m) or V(max) of l-alanine racemase or d-alanine-d-alanine synthetase of MAD-1 compared to its parent, CR34. MAD-1 is more susceptible to growth inhibition by penicillin or cycloserine than its parent, and is exquisitely sensitive to lysis in the presence of sodium deoxycholate or lysozyme. When cell wall biosynthesis is inhibited, MAD-1 lyses much more rapidly than CR34, even after it has been phenotypically suppressed by growth on d-alanine. The incorporation of l-alanine and diaminopimelic acid into the peptidoglycan of the mutant and wild type is identical; d-alanine is incorporated 1.5 times more rapidly into MAD-1 cells grown under nonpermissive conditions. The peptidoglycan fragments seen after digestion with lysozyme were similar for MAD-1 and the wild type. The results are interpreted as being compatible with an increased autolytic rate in MAD-1, caused either by an increase in the quantity or activity of an autolysin, or by an abnormal cell wall which is especially susceptible to autolysis, but which was not detected by analysis of peptidoglycan fragments.
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PMID:Relationship between permeability, cell division, and murein metabolism in a mutant of Escherichia coli. 426 3

Using heavily methionine-substituted T4 lysozyme as an example, it is shown how the addition or deletion of a small number of methionines can simplify the location of selenium sites for use in MAD phasing. By comparing the X-ray data for a large number of singly substituted lysozymes, it is shown that the optimal amino acid to be substituted by methionine is leucine, followed, in order of preference, by phenylalanine, isoleucine and valine. The identification of leucine as the first choice agrees with the ranking suggested by the Dayhoff mutation probability, i.e. by the frequency of amino-acid substitutions in the sequences of related proteins. The ranking of the second and subsequent choices, however, differ significantly.
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PMID:Use of differentially substituted selenomethionine proteins in X-ray structure determination. 1066 71

Single/multiple-wavelength anomalous dispersion (SAD/MAD) experiments were performed on a crystal of an organic arsenic derivative of hen egg-white lysozyme. A para-arsanilate compound used as a crystallizing reagent was incorporated into the ordered solvent region of the lysozyme molecule. Diffraction data were collected to high resolution (</=2.0 A) at three wavelengths around the K edge (1.04 A) of arsenic at beamline BM30A, ESRF synchrotron. Anomalous Patterson maps clearly showed the main arsanilate site to be between three symmetry-related lysozyme molecules, at a location previously occupied by a para-toluenesulfonate anion. MAD phases at 2 A derived using the program SHARP led to an electron-density map of sufficient quality to start manual building of the protein model. Amplitudes from a second crystal measured to a resolution of 1.8 A at the peak wavelength revealed two additional heavy-atom sites, which reinforced the anomalous subset model and therefore dramatically improved the phasing power of the arsenic derivative. The subsequent solvent-flattened map was of such high accuracy that the program ARP/wARP was able to build a nearly complete model automatically. This work emphasizes the great potential of arsenic for de novo structure determination using anomalous dispersion methods.
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PMID:Phasing power at the K absorption edge of organic arsenic. 1277 6

New methodologies with synchrotron radiation and X-ray free electron lasers (XFELs) in structural biology are being developed. Recent trends in harnessing softer X-rays in protein crystallography for phase determination are described. These include reference to a data-collection test at 2.6 A wavelength with a lysozyme crystal on SRS station 7.2 (Helliwell, 1983) and also use of softer X-rays (2 A wavelength) to optimise f " at the xenon L1 absorption edge in the Single Isomorphous Replacement Optimised Anomalous Scattering ('SIROAS') structure determination of apocrustacyanin A1 with four, partially occupied, xenon atoms (Cianci et al., 2001; Chayen et al., 2000). The hand of the protein was determined using the f " enhanced sulphur anomalous signal from six disulphides in the protein dimer of 40 kDa. In a follow-up study the single wavelength xenon L1-edge f " optimised data set alone was used for phase determination and phase improvement by solvent flattening etc. (CCP4 DM) (Olczak et al., 2003). Auto-tracing of the protein was feasible but required additional diffraction data at higher resolution. This latter could be avoided in future by using improved tilted detector settings during use of softer X-rays, i.e. towards back-scattering recording (Helliwell, 2002). The Olczak et al. study has already led to optimisation of the new SRS beamline MPW MAD 10 (see www.nwsgc.ac.uk) firstly involving the thinning of the beryllium windows as much as possible and planning for a MAR Research tilted detector 'desk top beamline' geometry. Thus the use of softer, i.e. 2 to 3 A wavelength range, X-rays will allow optimisation of xenon and iodine L-edge f " and enhancing of sulphur f " signals for higher throughput protein crystallography. Softer X-rays utilisation in protein crystallography includes work done on SRS bending-magnet station 7.2 in the early 1980s by the author as station scientist (Helliwell, 1984). In the future development of XFELs these softer X-ray wavelengths could also be harnessed and relax the demands to some extent on the complexity and cost of an XFEL. Thus, by use of say 4 A XFEL radiation and use of a back-scattering geometry area detector the single molecule molecular transform could be sampled to a spatial resolution of 2 A, sufficient, in principle, for protein model refinement (Miao et al., 1999). Meanwhile, Miao et al. (2003) report the first experimental recording of the diffraction pattern from intact Escherichia coli bacteria using coherent X-rays, with a wavelength of 2 A, at a resolution of 30 nm and a real-space image constructed. The new single-particle X-ray diffraction-imaging era has commenced.
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PMID:Overview and new developments in softer X-ray (2A < lambda < 5A) protein crystallography. 1464 19