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Ito N, Knowles PF, Phillips SE. X-ray crystallographic studies of cofactors in galactose oxidase. Methods Enzymol 1995; 258:235-62. [PMID: 8524154 DOI: 10.1016/0076-6879(95)58050-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Baron AJ, Stevens C, Wilmot C, Seneviratne KD, Blakeley V, Dooley DM, Phillips SE, Knowles PF, McPherson MJ. Structure and mechanism of galactose oxidase. The free radical site. J Biol Chem 1994; 269:25095-105. [PMID: 7929198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Crystallographic and spectroscopic studies on galactose oxidase have shown that the active site involves a free radical on tyrosine 272, one of the ligands coordinated to the Cu2+ cofactor. A novel thioether bond between tyrosine 272 and cysteine 228, and a stacking tryptophan 290, over this bond, are features of the crystal structure. The present study describes the development of a high level heterologous expression system for galactose oxidase and the construction of mutational variants at these key active site residues. The expressed wild-type enzyme and mutational variants (W290H and C228G) have been characterized by x-ray crystallography, visible spectroscopy, and catalytic activity measurements. A further variant protein, Y272F, could not be purified. The data establish that the thioether bond and stacking tryptophan are essential for activity and further support a role for tryptophan 290 as a component of the free radical site.
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Phillips SE. The beta-ribbon DNA recognition motif. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 1994; 23:671-701. [PMID: 7919796 DOI: 10.1146/annurev.bb.23.060194.003323] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Ito N, Phillips SE, Yadav KD, Knowles PF. Crystal structure of a free radical enzyme, galactose oxidase. J Mol Biol 1994; 238:794-814. [PMID: 8182749 DOI: 10.1006/jmbi.1994.1335] [Citation(s) in RCA: 272] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The crystal structure of the copper-containing enzyme, galactose oxidase, has been solved by multiple isomorphous replacement and refined to a resolution of 1.7 A. The X-ray structure reveals a unique polypeptide fold. The protein can be divided into three domains, all of which consist almost entirely of beta-strands. The structure of the second domain is particularly striking, 28 beta-strands arranged in a pseudo 7-fold symmetry. The copper site is on the surface of the protein and extremely rich in aromatic side-chains. The copper ion has two histidines, two tyrosines, and one external ligand in distorted square pyramidal coordination. The presence of pyrroloquinoline quinone as a covalently bound cofactor in GOase has been excluded. Instead, an unexpected covalent linkage between Tyr272 and Cys228 has been observed, whose functional role may relate to the presence of a tyrosine free radical at Tyr272. The tyrosine free radical could be stabilized by delocalization to Cys228 and stacking interactions with Trp290. A structural model for substrate binding is proposed that offers an explanation for the substrate specificity of the enzyme and many of the spectroscopic and enzymological data. Although the model lacks direct confirmation at present, it should provide a stimulus for further spectroscopic and crystallographic studies.
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Abstract
BACKGROUND The three-dimensional structure of the Escherichia coli methionine repressor (met repressor) is relatively unperturbed by the binding of its corepressor, S-adenosylmethionine (SAM), and of operator DNA. The positively charged corepressor binds to sites on the repressor remote from the DNA-binding site, and despite the lack of induced structural change is able to raise the affinity for operator DNA by a factor of up to 1000. Neutral corepressor analogues also bind to the repressor, but do not increase operator affinity. These observations suggest that the corepressor effect may be electrostatic. RESULTS Using the program DELPHI, we have calculated electrostatic potentials for the repressor and its complexes, and have obtained results consistent with an electrostatic model for repressor activation. The positive potential originating from the corepressor is propagated through the repressor-operator complex, and is significant at DNA phosphate groups buried in the protein-DNA interface. The rank order of calculated electrostatic interaction energies for complexes with SAM, and two closely-related analogues, is in agreement with experimental measurements of the corresponding repressor-operator affinities. CONCLUSION Long-range (> 10 A) electrostatic interactions between bound corepressor and operator phosphate groups in the repressor-operator complex may be sufficient to explain repressor activation Met repressor could, therefore, be an electrostatically triggered genetic switch.
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Schneider DA, Phillips SE, Stoffolano S. The simplified V-slope method of detecting the gas exchange threshold. Med Sci Sports Exerc 1993; 25:1180-4. [PMID: 8231764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A simplified V-slope method was used to visually determine the first point of departure from linearity of carbon dioxide output (VCO2) plotted against oxygen uptake (VO2). The point at which VCO2 departed from a line with a slope equal to 1.00 was visually selected as the gas exchange threshold during incremental exercise. The simplified method of threshold detection was compared with a computerized V-slope method. Both methods were used to determine the gas exchange threshold during incremental cycling (10 W.min-1) in 17 untrained female subjects. The thresholds occurred at 41.1% and 45.1% of VO2max using the computerized and simplified V-slope methods, respectively. The correlation between the oxygen uptake measured at the threshold using the two methods was 0.95. Power output, VO2, and heart rate values determined at the gas exchange threshold using the simplified V-slope method were significantly higher than the corresponding values obtained using the computerized V-slope method. The simplified V-slope method consistently placed the gas exchange threshold at the work rate that was about 10 W above the power output determined by the computerized method. Although the two methods were highly correlated, the simplified V-slope method tended to overestimate threshold values determined from a computerized gas exchange method.
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Brothman AR, Newlin A, Phillips SE, Kinzie GQ, Leichtman LG. Prenatal detection of an inverted X chromosome in a male. Clin Genet 1993; 44:139-41. [PMID: 8275571 DOI: 10.1111/j.1399-0004.1993.tb03864.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
An unusual case of an X chromosome with a pericentric inversion (p11.3q21.3) was detected prenatally in a male fetus. This inversion has not been previously characterized. Although the inverted chromosome was transmitted through the mother, no living males on the maternal side were detected with the aberrant chromosome. Replication studies were performed on cultures of maternal peripheral blood lymphocytes, and it was determined that the inverted X chromosome was early replicating in approximately half of the cells. Following genetic counseling, the pregnancy was continued and a healthy male infant was delivered at term. Cytogenetic analysis of peripheral blood performed in the newborn period confirmed the prenatal findings. The child is developing normally at 3 years of age.
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McPherson MJ, Stevens C, Baron AJ, Ogel ZB, Seneviratne K, Wilmot C, Ito N, Brocklebank I, Phillips SE, Knowles PF. Galactose oxidase: molecular analysis and mutagenesis studies. Biochem Soc Trans 1993; 21 ( Pt 3):752-6. [PMID: 8224504 DOI: 10.1042/bst0210752] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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63
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Parsons DS, Phillips SE. Functional endoscopic surgery in children: a retrospective analysis of results. Laryngoscope 1993; 103:899-903. [PMID: 8361292 DOI: 10.1288/00005537-199308000-00011] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The impact of chronic sinusitis on children has become more apparent as the awareness of the disease has increased. Consequently, the knowledge of its effect in the pediatric patient has expanded dramatically. Functional endoscopic sinus surgery (FESS) has become the primary surgical modality for treatment of this illness in children who have not responded to optimal medical management. A retrospective study was conducted in patients from 7 months to 17 years of age who were treated with FESS for chronic sinusitis refractory to medical therapy. Using a comprehensive parental questionnaire and a review of the medical charts, results were analyzed from these post-FESS children. Parents of the children were interviewed with a mean follow-up time of 21.8 months postoperatively. Factors discussed included chronic nasal obstruction, purulent nasal discharge, postnasal drip, chronic cough, halitosis, headaches, behavioral problems, allergies, and asthma symptoms. This preliminary investigation suggests that FESS is effective in treating medically recalcitrant severe chronic sinusitis in children.
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Baron AJ, Stevens C, Wilmot CM, Knowles PF, Phillips SE, McPherson MJ. Preliminary studies of two active site mutants of galactose oxidase. Biochem Soc Trans 1993; 21 ( Pt 3):319S. [PMID: 8224464 DOI: 10.1042/bst021319s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Fugate DJ, Clarizio HF, Phillips SE. Referral-to-placement ratio: a finding in need of reassessment? JOURNAL OF LEARNING DISABILITIES 1993; 26:413-416. [PMID: 8354945 DOI: 10.1177/002221949302600607] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Previous research has reported that the number of evaluated children placed in special education is as high as three out of four. The purpose of the present study is to reassess, extend, and update referral-to-placement research. Subjects consisted of 236 predominantly white children referred for special education evaluation from 12 suburban and rural school districts. Of the 236 pupils referred, 128 were diagnosed as learning disabled (LD) by a multidisciplinary team (MDT). The 128 students identified as eligible for services for students with LD had a mean IQ of 96.43 and a mean age of 10.2. The majority of the subjects were male (70%). The results suggest that the number of students referred who are actually placed is lower (approximately one out of two) than previously reported. It is concluded that further research is needed to verify the current referral-to-placement ratio and to explore the factors influencing this ratio.
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Böcskei Z, Groom CR, Flower DR, Wright CE, Phillips SE, Cavaggioni A, Findlay JB, North AC. Pheromone binding to two rodent urinary proteins revealed by X-ray crystallography. Nature 1992; 360:186-8. [PMID: 1279439 DOI: 10.1038/360186a0] [Citation(s) in RCA: 286] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The principal protein excreted in male rat urine, urinary alpha 2-globulin and the homologous mouse protein, major urinary protein, have been well characterized, although their functions remain unclear. Male rat urine affects the behaviour and sexual response of female rats, leading to the proposal that rodent urinary proteins are responsible for binding pheromones and their subsequent release from drying urine. Urinary alpha 2-globulin is also involved in hyaline droplet nephropathy, an important toxicological syndrome in male rats resulting from exposure to a number of industrial chemicals and characterized by the accumulation of liganded urinary alpha 2-globulin in lysosomes in the kidney, followed by the induction of renal cancer. We now report the three-dimensional structures of mouse major urinary protein (at 2.4 A resolution) and rat urinary alpha 2-globulin (at 2.8 A resolution). The results corroborate the role of these proteins in pheromone transport and elaborate the structural basis of ligand binding.
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He YY, McNally T, Manfield I, Navratil O, Old IG, Phillips SE, Saint-Girons I, Stockley PG. Probing met repressor-operator recognition in solution. Nature 1992; 359:431-3. [PMID: 1406957 DOI: 10.1038/359431a0] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The three-dimensional crystal structure of the Escherichia coli methionine repressor, MetJ, complexed with a DNA operator fragment is described in an accompanying article. The complex exhibits several novel features of DNA-protein interaction. DNA sequence recognition is achieved largely by hydrogen-bond contacts between the bases and amino-acid side chains located on a beta-ribbon, a mode of recognition previously hypothesized on the basis of modelling of idealized beta-strands and DNA, and mutagenesis of the Salmonella phage P22 repressors Arc and Mnt. The complex comprises a pair of MetJ repressor dimers which bind to adjacent met-box sites on the DNA, and contact each other by means of a pair of antiparallel alpha-helices. Here we assess the importance of these contacts, and also of contacts that would be made between the C-helices of the protein and DNA in a previous model of the complex, by studying mutations aimed at disrupting them. The role of the carboxy-terminal helix face in operator binding was unclear, but we demonstrate that recognition of operator sequences occurs through side chains in the beta-strand motif and that dimer-dimer interactions are required for effective repression.
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Somers WS, Phillips SE. Crystal structure of the met repressor-operator complex at 2.8 A resolution reveals DNA recognition by beta-strands. Nature 1992; 359:387-93. [PMID: 1406951 DOI: 10.1038/359387a0] [Citation(s) in RCA: 237] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The crystal structure of the met repressor-operator complex shows two dimeric repressor molecules bound to adjacent sites 8 base pairs apart on an 18-base-pair DNA fragment. Sequence specificity is achieved by insertion of double-stranded antiparallel protein beta-ribbons into the major groove of B-form DNA, with direct hydrogen-bonding between amino-acid side chains and the base pairs. The repressor also recognizes sequence-dependent distortion or flexibility of the operator phosphate backbone, conferring specificity even for inaccessible base pairs.
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Brothman AR, Rehberg K, Storto PD, Phillips SE, Mosby RT. Confirmation of true mosaic trisomy 20 in a phenotypically normal liveborn male. Clin Genet 1992; 42:47-9. [PMID: 1516227 DOI: 10.1111/j.1399-0004.1992.tb03136.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A new case of prenatally detected mosaic trisomy 20 (79% trisomy 20 cells in amniocyte cultures) that was confirmed in newborn tissue is presented. A healthy male infant was delivered at term, with no dysmorphology or apparent malformations; this baby is developing normally. Twenty-five percent of foreskin and 17% of fetal cord cells also showed trisomy 20, while no trisomic cells were detected in newborn blood. High frequency mosaicism for trisomy 20 in this case was thus due to true embryonic origin. Extensive counseling and prenatal follow-up in this case led to an unaffected liveborn, and guarded optimism may be warranted for future cases of mosaic trisomy 20 detected prenatally.
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Wright CE, Rafferty JB, Flower DR, Groom CR, Findlay JB, North AC, Phillips SE, Zagalsky PF. Crystallization and initial X-ray analysis of the C2-subunit of crustacyanin. J Mol Biol 1992; 224:283-4. [PMID: 1548709 DOI: 10.1016/0022-2836(92)90594-a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Crystals of the C2-subunit of crustacyanin have been grown from solutions containing ammonium sulphate and 2-methyl-2,4-pentanediol as co-precipitants. The crystals belong to space group P2(1)2(1)2(1) (a = 42.0 A, b = 80.9 A, c = 110.8 A) with two subunits per asymmetric unit and diffract beyond 2.2 A resolution.
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Ito N, Phillips SE, Stevens C, Ogel ZB, McPherson MJ, Keen JN, Yadav KD, Knowles PF. Three-dimensional structure of galactose oxidase: an enzyme with a built-in secondary cofactor. Faraday Discuss 1992:75-84. [PMID: 1290941 DOI: 10.1039/fd9929300075] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Galactose oxidase is a copper-containing enzyme, which catalyses stereospecific oxidation of primary alcohols. The three-dimensional structure of the enzyme has been determined in this study by X-ray crystallography at high resolution. The molecule is almost entirely composed of beta-structures and consists of three domains. The arrangement of 28 beta-strands in the second domain is of particular interest, having seven four-stranded antiparallel beta-sheets with pseudo-sevenfold symmetry. The copper site has square-pyramidal coordination with two histidines, one tyrosine and one exogenous ligand at the equatorial sites and another tyrosine at the axial site. The most intriguing structural feature is a covalent bond between C epsilon 1 of Tyr-272, which is one of the equatorial ligands, and S gamma of Cys-228. This unexpected thioether bond, and Trp-290 stacked above it, strongly supports the presence of a tyrosine free radical in the enzyme as a 'built-in' secondary cofactor. Calculation of the molecular surface shows a small pocket at the copper site and suggests a substrate-binding model, which can explain the substrate specificity. A model for the catalytic mechanism, involving a tyrosine free radical and basic tryptophan, is also proposed.
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Fischmann TO, Bentley GA, Bhat TN, Boulot G, Mariuzza RA, Phillips SE, Tello D, Poljak RJ. Crystallographic refinement of the three-dimensional structure of the FabD1.3-lysozyme complex at 2.5-A resolution. J Biol Chem 1991; 266:12915-20. [PMID: 1712773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The three-dimensional crystal structure of the complex between the Fab from the monoclonal anti-lysozyme antibody D1.3 and the antigen, hen egg white lysozyme, has been refined by crystallographic techniques using x-ray intensity data to 2.5-A resolution. The antibody contacts the antigen with residues from all its complementarity determining regions. Antigen residues 18-27 and 117-125 form a discontinuous antigenic determinant making hydrogen bonds and van der Waals interactions with the antibody. Water molecules at or near the antigen-antibody interface mediate some contacts between antigen and antibody. The fine specificity of antibody D1.3, which does not bind (K alpha less than 10(5) M-1) avian lysozymes where Gln121 in the amino acid sequence is occupied by His, can be explained on the basis of the refined model.
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Böcskei Z, Findlay JB, North AC, Phillips SE, Somers WS, Wright CE, Lionetti C, Tirindelli R, Cavaggioni A. Crystallization of and preliminary X-ray data for the mouse major urinary protein and rat alpha-2u globulin. J Mol Biol 1991; 218:699-701. [PMID: 1708830 DOI: 10.1016/0022-2836(91)90258-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Crystals of the mouse major urinary protein (MUP) and rat alpha-2u globulin (AMG) have been grown from solutions of polyethylene glycol 3350 and CdCl2, respectively. The crystals differ both in their morphologies and space groups but have very similar unit cell sizes. AMG crystallized in P2(1) (a = 56.6 A, b = 103.8 A, c = 62.7 A, beta = 95.1 degrees) with four subunits/asymmetric unit, while MUP gave crystals in P4(1)2(1)2 or P4(3)2(1)2 (a = 57.3 A, c = 109.9 A) with one subunit/asymmetric unit. Both crystal forms diffract beyond 2.8 A resolution.
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Ito N, Phillips SE, Stevens C, Ogel ZB, McPherson MJ, Keen JN, Yadav KD, Knowles PF. Novel thioether bond revealed by a 1.7 A crystal structure of galactose oxidase. Nature 1991; 350:87-90. [PMID: 2002850 DOI: 10.1038/350087a0] [Citation(s) in RCA: 556] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Galactose oxidase is an extracellular enzyme secreted by the fungus Dactylium dendroides. It is monomeric, with a relative molecular mass of 68,000, catalyses the stereospecific oxidation of a broad range of primary alcohol substrates and possesses a unique mononuclear copper site essential for catalysing a two-electron transfer reaction during the oxidation of primary alcohols to corresponding aldehydes. Recent evidence arguing against a Cu(III)-Cu(I) couple implies the existence of a second redox-active site proposed to involve pyrroloquinoline quinone or a tyrosine radical. We now report the crystal structure of galactose oxidase at 1.7 A resolution. This reveals a unique structural feature at the copper site with a novel thioether bond linking Cys 228 and Tyr 272 in a stacking interaction with Trp 290. We propose that these molecular components stabilize the protein free-radical species essential for catalysis and thus provide a 'built-in' secondary cofactor. This feature may represent a new mechanism for mediating electron transfer in metalloenzymes in the absence of exogenous cofactors.
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Old IG, Phillips SE, Stockley PG, Saint Girons I. Regulation of methionine biosynthesis in the Enterobacteriaceae. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1991; 56:145-85. [PMID: 1771231 DOI: 10.1016/0079-6107(91)90012-h] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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