1351
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Yu X, Matsuda Z, Yu QC, Lee TH, Essex M. Vpx of simian immunodeficiency virus is localized primarily outside the virus core in mature virions. J Virol 1993; 67:4386-90. [PMID: 8510227 PMCID: PMC237811 DOI: 10.1128/jvi.67.7.4386-4390.1993] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Human immunodeficiency virus type 2 and the related simian immunodeficiency virus (SIV) contain a unique regulatory gene, vpx. The Vpx protein is packaged in mature virions and is required for efficient viral replication in peripheral blood lymphocytes and macrophages. To study the localization of Vpx in mature virions, conical and bar-shaped core structures of SIV from macaques (SIVmac) were purified. The SIVmac core has a density of approximately 1.25 g/cm3, compared with 1.16 g/cm3 for an intact virion. The relative proportions of major capsid protein (p27) and reverse transcriptase activity were similar for intact virions and core structures. The majority of matrix protein (p14) was removed from the purified core structure, suggesting its association with the viral membrane. Similarly, most of the Vpx protein was absent from the purified core structure. This result suggests that as with the matrix protein, the majority of Vpx proteins are localized outside the virus core. The localization of Vpx suggests that it may be involved in virus entry such as penetration or uncoating.
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1352
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Yu X, Ma Q. [Fermentation of engineered strain producing cholera toxin B subunit]. WEI SHENG WU XUE BAO = ACTA MICROBIOLOGICA SINICA 1993; 33:177-81. [PMID: 8236951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Studies indicate that the cholera B subunit could be synthesized efficiently in corn steep liquor by engineered E. coli strain MM2. We have also determined the optical density, pH and the yield of B subunit kinetically during fermentation. Corn steep liquor medium has advantages in low cost, simplicity in technological process and high yield of B subunit which can reaches 40 micrograms/ml in 50L fermentative tank.
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1353
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Davis EL, Yu X, Joynt RB, Wieczkowski G, Giordano L. Shear strength and microleakage of light-cured glass ionomers. AMERICAN JOURNAL OF DENTISTRY 1993; 6:127-9. [PMID: 8240773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Bond to dentin and marginal integrity of three light activated glass ionomer cements were evaluated, and compared to a traditional chemical-cured glass ionomer cement. Results indicated no significant difference in shear bond strength among the glass ionomer cements tested. However, there was a significant difference among glass ionomer cements in bond strength variability, with coefficients of variation ranging from 55 to 102%. A discrepancy between manufacturers' instructions and optimum curing times is one possible explanation for these results. There were also no significant differences in microleakage among glass ionomer cements. Most samples exhibited minimal or no microleakage.
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1354
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Yu X, Wojciechowski M, Fenselau C. Assessment of metals in reconstituted metallothioneins by electrospray mass spectrometry. Anal Chem 1993; 65:1355-9. [PMID: 8517548 DOI: 10.1021/ac00058a010] [Citation(s) in RCA: 133] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A method has been developed that combines electrospray ionization mass spectrometry with pH control to provide analysis of metals in native or reconstituted metallothioneins. These metalloproteins cooperatively bind seven divalent metal ions, most commonly Zn2+ and Cd2+. Since the protein is denatured and metal ions are lost below pH3, the pH of the electrospray solution is critical to successful results. The metal-free apoprotein was detected with its most abundant ions in a charge state of 6+, while the folded metallothionein-metal complexes were observed with lower charge states. The retention of seven metals in the molecular ions detected is consistent with the hypothesis that metallothionein retains its conformation in the gas phase. This mass spectrometric technique can be used to determine rapidly and accurately how many and what cations are incorporated per molecule of protein. Information about molar distributions and estimates of relative abundances of various complexes in the sample can be acquired in a single measurement.
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1355
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Yu X, Egelman EH. The LexA repressor binds within the deep helical groove of the activated RecA filament. J Mol Biol 1993; 231:29-40. [PMID: 8496964 DOI: 10.1006/jmbi.1993.1254] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The RecA protein of Escherichia coli, as a result of DNA damage, catalyzes the cleavage of its own repressor, the LexA protein, and thereby initiates the SOS response. Using a non-cleavable LexA mutant, we have obtained a co-complex of both the RecA and LexA proteins on DNA. Mass analysis using scanning transmission electron microscopy suggests that the site size of the LexA repressor on RecA is two, which would be consistent with a nearest-neighbor exclusion model for binding. Three-dimensional reconstruction of electron micrographs of these filaments shows that the LexA protein is bound in the deep groove of the RecA filament, with two strong regions of contact that span adjacent RecA protomers within the filament. One contact is consistent with a proposed LexA binding site in the RecA crystal structure. The other contact maps onto a region that has been postulated to be a second DNA-binding site within RecA, which can explain the inhibition of RecA cleavage of LexA by excess DNA.
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1356
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North WG, Yu X. Forms of neurohypophysial peptides generated by tumors, and factors regulating their expression. REGULATORY PEPTIDES 1993; 45:209-16. [PMID: 8390078 DOI: 10.1016/0167-0115(93)90208-p] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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1357
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Matsuda Z, Yu X, Yu QC, Lee TH, Essex M. A virion-specific inhibitory molecule with therapeutic potential for human immunodeficiency virus type 1. Proc Natl Acad Sci U S A 1993; 90:3544-8. [PMID: 7682710 PMCID: PMC46337 DOI: 10.1073/pnas.90.8.3544] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A potential new approach for gene therapy against human immunodeficiency virus type 1 (HIV-1) infection is the design of a nonstructural gene-based virion-specific inhibitory molecule that is packaged with virus to destroy its infectivity. We tested this approach for HIV-1 by using Vpx, a virion-associated protein of HIV-2 and simian immunodeficiency virus. Vpx was incorporated into HIV-1 virions and the resulting cell-free virus lost infectivity in CD4+ human T cells. This demonstrates the therapeutic potential of an accessory gene-based virion-specific inhibitory molecule. Vpx and its derivatives can be regarded as a new class of anti-HIV-1 molecule.
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1358
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Yu X, Carroll S, Rigaud JL, Inesi G. H+ countertransport and electrogenicity of the sarcoplasmic reticulum Ca2+ pump in reconstituted proteoliposomes. Biophys J 1993; 64:1232-42. [PMID: 8388268 PMCID: PMC1262440 DOI: 10.1016/s0006-3495(93)81489-9] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The Ca2+ transport adenosine triphosphatase of sarcoplasmic reticulum was reconstituted in unilamellar liposomes prepared by reverse-phase evaporation. The size of the resulting proteoliposomes was similar to that of native sarcoplasmic reticulum vesicles, but their protein content was much lower, with a protein/lipid ratio (wt/wt) of 1:40-160, as compared with 1:1 in the native membrane. The proteoliposomes sustained adenosine triphosphate-dependent Ca2+ uptake at rates proportional to the protein content (1-2 mumol Ca2+/mg protein/min), reaching asymptotic levels corresponding to a lumenal calcium concentration of 10-20 mM. The low permeability of the proteoliposomes permitted direct demonstration of Ca2+/H+ countertransport and electrogenicity by parallel measurements in the same experimental system. Countertransport of one H+ per one Ca2+ was demonstrated, and inhibition of the Ca2+ pump by lumenal alkalinization was relieved by the H+ ionophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone. Consistent with the countertransport stoichiometry, net positive charge displacement was produced by Ca2+ transport, as revealed by a rapid oxonol VI absorption rise. The initial rise and the following steady-state level of oxonol absorption were highest when SO4(2-) was the prevalent anion and lowest in the presence of the lipophilic anion SCN-. The influence of anions was attributed to potential driven counterion compensation. The absorption rise was rapidly collapsed by addition of valinomycin in the presence of K+. Experimentation with Ca2+ and H+ ionophores was consistent with a primary role of Ca2+ and H+ in net charge displacement. The estimated value of the steady-state electrical potential observed under optimal conditions was approximately 50 mV and was accounted for by the estimated charge transfer associated with Ca2+ and H+ countertransport under the same conditions.
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1359
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Ogawa T, Yu X, Shinohara A, Egelman EH. Similarity of the yeast RAD51 filament to the bacterial RecA filament. Science 1993; 259:1896-9. [PMID: 8456314 DOI: 10.1126/science.8456314] [Citation(s) in RCA: 521] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The RAD51 protein functions in the processes of DNA repair and in mitotic and meiotic genetic recombination in the yeast Saccharomyces cerevisiae. The protein has adenosine triphosphate-dependent DNA binding activities similar to those of the Escherichia coli RecA protein, and the two proteins have 30 percent sequence homology. RAD51 polymerized on double-stranded DNA to form a helical filament nearly identical in low-resolution, three-dimensional structure to that formed by RecA. Like RecA, RAD51 also appears to force DNA into a conformation of approximately a 5.1-angstrom rise per base pair and 18.6 base pairs per turn. As in other protein families, its structural conservation appears to be stronger than its sequence conservation. Both the structure of the protein polymer formed by RecA and the DNA conformation induced by RecA appear to be general properties of a class of recombination proteins found in prokaryotes as well as eukaryotes.
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1360
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Yu X, Reed BM. Improved shoot multiplication of mature hazelnut (Corylus avellana L.) in vitro using glucose as a carbon source. PLANT CELL REPORTS 1993; 12:256-259. [PMID: 24197152 DOI: 10.1007/bf00237130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/1992] [Revised: 12/11/1992] [Indexed: 06/02/2023]
Abstract
Shoot cultures established from mature trees of hazelnut (Corylus avellana L.) cvs. Nonpareil and Tonda Gentile Romana were used to determine the effects of basal media, carbon sources and concentrations, pH and cytokinins on shoot multiplication. All factors except pH affected the multiplication rate. Shoot multiplication was the best on a modified Driver and Kuniyuki medium for Paradox walnut (DKW) supplemented with 6-benzylaminopurine (BA) (1.5-3 mg/l). Plants grown on 3% glucose or fructose medium produced more and longer shoots than those on sucrose. The general appearance and growth habit of shoots were better on medium with glucose than fructose. 'Nonpareil' shoots elongated better than those of 'Tonda Gentile Romana.' Changes in medium pH from 4.7 to 5.7 did not significantly affect the multiplication rate. More than 10 genotypes propagated well on modified DKW medium with glucose. This is the first report of the effect of carbon sources on shoot multiplication of hazelnut and provides a basis for further research in the improvement of hazelnut micropropagation.
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1361
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Yu X, Chung M, Morabito MA, Barnstable CJ. Shared nuclear protein binding sites in the upstream region of the rat opsin gene. Biochem Biophys Res Commun 1993; 191:76-82. [PMID: 7916602 DOI: 10.1006/bbrc.1993.1186] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
DNase I protection and gel retardation assays have identified two sequences 5' to the rat opsin gene that interact with nuclear proteins from retina but not from a number of neuronal and non-neuronal tissues. These sites, Ret 2 and Ret 3, are over 1200 base pairs apart but seem to interact with the same protein(s). Synthetic oligonucleotides corresponding to each site were able to inhibit complex formation in a gel retardation assay using an oligonucleotide corresponding to the other site. The proteins binding to the Ret 2 and Ret 3 sites co-eluted in both ion exchange and gel filtration chromatography. The protein(s) were also present at adult levels at birth, suggesting that they may represent differentiation products expressed in the proliferating retinal epithelium.
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1362
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Doige CA, Yu X, Sharom FJ. The effects of lipids and detergents on ATPase-active P-glycoprotein. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1146:65-72. [PMID: 8095161 DOI: 10.1016/0005-2736(93)90339-2] [Citation(s) in RCA: 154] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We previously isolated and characterized a partially purified preparation of ATPase-active P-glycoprotein, the multidrug transporter (Doige, C.A., Yu, X. and Sharom, F.J. (1992) Biochim. Biophys. Acta 1109, 149-160). The effect of various detergents and membrane phospholipids on the ATPase activity of P-glycoprotein has now been investigated. P-Glycoprotein ATPase activity was most stable in CHAPS, with over 50% of the activity retained at a concentration of 8 mM. Octyl glucoside in the low mM range also supported the ATPase, while deoxycholate destroyed all activity at 1 mM. Digitonin and SDS inhibited ATPase activity at very low concentrations. Triton X-100 at 2-10 microM stimulated the ATPase almost 2-fold, while higher levels inhibited activity. Although P-glycoprotein ATPase was sensitive to thermal inactivation, full activity was preserved in the presence of asolectin, but not phosphatidylcholine species. Further studies revealed that asolectin, both saturated and unsaturated phosphatidylethanolamines, and phosphatidylserine, were best able to maintain ATPase activity at 23 degrees C. Saturated phosphatidylethanolamine species activated P-glycoprotein ATPase up to 40% at 23 degrees C, and 80% at 4 degrees C. Following detergent delipidation, various lipids were able to restore P-glycoprotein ATPase activity. Unsaturated phosphatidylcholine and phosphatidylserine were most effective, while saturated species were not able to restore catalytic activity. These results indicate that membrane lipids are necessary for catalytic activity of the ATPase domains of P-glycoprotein. P-Glycoprotein has well-defined lipid preferences, with saturated phosphatidylethanolamines both activating the ATPase and providing protection from thermal inactivation, while fluid lipid mixtures are able to restore activity following delipidation.
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1363
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Jones CE, Beise EJ, Belz JE, Carr RW, Filippone BW, Lorenzon W, McKeown RD, Mueller BA, O'Neill TG, Dodson GW, Dow K, Farkhondeh M, Kowalski S, Lee K, Makins N, Milner R, Thompson A, Tieger D, Young A, Yu X, Zumbro JD. He-vector3(e-vectore') quasielastic asymmetry. PHYSICAL REVIEW. C, NUCLEAR PHYSICS 1993; 47:110-130. [PMID: 9968416 DOI: 10.1103/physrevc.47.110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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1364
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Yu X, Yuan X, McLane MF, Lee TH, Essex M. Mutations in the cytoplasmic domain of human immunodeficiency virus type 1 transmembrane protein impair the incorporation of Env proteins into mature virions. J Virol 1993; 67:213-21. [PMID: 8416370 PMCID: PMC237354 DOI: 10.1128/jvi.67.1.213-221.1993] [Citation(s) in RCA: 117] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In-frame stop codons were introduced into the coding region of human immunodeficiency virus type 1 (HIV-1) transmembrane protein (gp41). Truncation of 147 amino acids from the carboxyl terminus of gp41 (TM709) significantly decreased the stability and cell surface expression of the viral Env proteins, while truncation of 104 amino acids (TM752) did not. Truncation of 43 or more amino acids from the carboxyl terminus of gp41 generated mutant viruses which were noninfectious in several human CD4+ T lymphoid cell lines and fresh peripheral blood mononuclear cells. Analysis of the noninfectious mutant virions revealed significantly reduced incorporation of the Env proteins compared with the wild-type virions. Comparable amounts of Env proteins were detected on the surfaces of wild-type- and TM752-transfected cells, suggesting that the structures of gp41 required for efficient incorporation of Env proteins were disrupted in mutant TM752. Truncation of the last 12 amino acids (TM844) from the carboxyl terminus of gp41 did not significantly affect the assembly and release of virions or the incorporation of Env proteins into mature virions. However, the TM844 virus had dramatically decreased infectivity compared with the wild-type virus. This suggests that the cytoplasmic domain of gp41 also plays a role in other steps of virus replication.
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1365
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Ogawa T, Shinohara A, Nabetani A, Ikeya T, Yu X, Egelman EH, Ogawa H. RecA-like recombination proteins in eukaryotes: functions and structures of RAD51 genes. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 1993; 58:567-76. [PMID: 7956071 DOI: 10.1101/sqb.1993.058.01.063] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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1366
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Yu X, Jin Y, Fan M, Xu G, Liu Q, Raoult D. Genotypic and antigenic identification of two new strains of spotted fever group rickettsiae isolated from China. J Clin Microbiol 1993; 31:83-8. [PMID: 8093253 PMCID: PMC262626 DOI: 10.1128/jcm.31.1.83-88.1993] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Four isolates of spotted fever group rickettsiae isolated from ticks in China were compared with all known species and strains of spotted fever group rickettsiae by immunofluorescence assay, DNA polymerase chain reaction followed by restriction endonuclease fragment length polymorphism analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western immunoblot. The Chinese isolates belonged to three types, including a novel serotype which has not been described before. One isolate obtained from tick ova of Dermacentor nuttallii in Inner Mongolia was antigenically and genotypically identical to Rickettsia sibirica. Two isolates obtained from Dermacentor sinicus collected from Beijing were identical, different from other members of spotted fever group rickettsiae but apparently closely related to R. sibirica. HA-91, a strain isolated from Hyalomma asiaticum bv. kozlovi olenew, was antigenically and genotypically unique among spotted fever group rickettsiae, and we feel that data presented here should prompt consideration of it as a new species on the basis of current rickettsial taxonomy.
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1367
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Inesi G, Cantilina T, Yu X, Nikic D, Sagara Y, Kirtley ME. Long-range intramolecular linked functions in activation and inhibition of SERCA ATPases. Ann N Y Acad Sci 1992; 671:32-47; discussion 48. [PMID: 1288328 DOI: 10.1111/j.1749-6632.1992.tb43782.x] [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: 12/26/2022]
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1368
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Miller DE, Noble NA, Yu X, Border WA. Molecular and cellular biological techniques in the study of glomerular diseases. Semin Nephrol 1992; 12:506-15. [PMID: 1282274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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1369
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Doige CA, Yu X, Sharom FJ. ATPase activity of partially purified P-glycoprotein from multidrug-resistant Chinese hamster ovary cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 1992; 1109:149-60. [PMID: 1355666 DOI: 10.1016/0005-2736(92)90078-z] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In vitro studies of multidrug-resistant cell lines have shown that a membrane protein, the P-glycoprotein, is responsible for resistance to a wide range of structurally and functionally dissimilar anti-cancer drugs. The amino-acid sequence of P-glycoprotein (Pgp) indicates two consensus sequences for ATP binding and the purified protein has been reported to possess a low level of ATPase activity. As part of our goal to further characterize the ATPase activity of P-glycoprotein, we have developed a procedure for rapid partial purification of the protein in a highly active form. Plasma membrane vesicles from multidrug-resistant CHRC5 Chinese hamster ovary cells were subjected to a two-step procedure involving selective extraction with different concentrations of the zwitterionic detergent CHAPS. The resulting extract was enriched in P-glycoprotein (around 30% pure) and displayed an ATPase activity (specific activity 543 nmol mg-1 min-1) that was not found in a similar preparation from drug-sensitive cells. The ATPase specific activity was over 10-fold higher than that previously reported for immunoprecipitated Pgp and 280-fold higher than that of immunoaffinity-purified Pgp. This ATPase activity could be distinguished from that of other ion-motive ATPases and membrane-associated phosphatases and is, thus, proposed to be directly attributable to P-glycoprotein. Optimal P-glycoprotein ATPase activity required Mg2+ at an ATP: Mg2+ molar ratio of 0.75:1 and the apparent Km for ATP was 0.88 mM. P-Glycoprotein ATPase could be completely inhibited by vanadate and by the sulfhydryl-modifying reagents N-ethylmaleimide, HgCl2 and p-chloromercuribenzenesulfonate. Certain drugs and chemosensitizers, including colchicine, progesterone, nifedipine, verapamil and trifluoperazine, produced up to 50% activation of P-glycoprotein ATPase activity.
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1370
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Yu X, Egelman EH. Structural data suggest that the active and inactive forms of the RecA filament are not simply interconvertible. J Mol Biol 1992; 227:334-46. [PMID: 1522597 DOI: 10.1016/0022-2836(92)90702-l] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have used electron microscopy to examine the two major conformational states of the helical filament formed by the RecA protein of Escherichia coli. The compressed filament, formed in the absence of a nucleotide cofactor either as a self-polymer or on a single-stranded DNA molecule, is characterized in solution by about 6.1 subunits per turn of a 76 A pitch helix, and appears to be inactive with respect to all RecA activity. The active state of the filament, formed with ATP or an ATP analog on either a single or double-stranded DNA substrate, has about 6.2 subunits per turn of a 94 A pitch helix. Measurements of the contour length of RecA-covered single-stranded DNA circles in ice, formed in the absence of nucleotide cofactor, indicate that each RecA subunit binds five bases, in contrast to the three bases or base-pairs per subunit in the active state. The different stoichiometries of DNA binding suggests that the two polymeric forms are not interconvertible, as has been suggested on biochemical grounds. A three-dimensional reconstruction of the inactive state shows the same general features as the 83 A pitch filament present in the RecA crystal. This structural similarity and the fact that the crystal does not contain ATP or DNA suggests that the crystal structure is more similar to the compressed filament than the active, extended filament.
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1371
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Yu X, Yu QC, Lee TH, Essex M. The C terminus of human immunodeficiency virus type 1 matrix protein is involved in early steps of the virus life cycle. J Virol 1992; 66:5667-70. [PMID: 1501299 PMCID: PMC289135 DOI: 10.1128/jvi.66.9.5667-5670.1992] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Deletion mutations at the C terminus of the matrix (MA) protein of human immunodeficiency virus type 1 (HIV-1) were generated by site-directed mutagenesis. The resultant mutant viruses had a severe defect in virus infectivity. This defect did not involve late steps of the virus life cycle, as the synthesis and processing of the Gag polyprotein and the assembly and release of mutant virions were not greatly affected. The incorporation of viral proteins and the viral RNA genome was similar for mutant and wild-type virions. In contrast, the early steps of the virus life cycle were severely affected, as the synthesis of viral DNA postinfection was dramatically reduced in mutant-virus-infected cells. One stretch of amino acids that was deleted in one of the mutants has significant homology with a region in VP1 of the picornavirus family. This region of VP1 is presumably involved in poliovirus penetration into cells. These results suggest that in addition to its functional role in virus assembly, the MA protein of HIV-1, and possibly of other retroviruses, plays an important role in virus entry.
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1372
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Haugstad G, Raisanen A, Yu X, Vanzetti L, Franciosi A. Photoemission study of adsorbed Xe on GaAs(110), HgTe(110), and Hg1-xCdxTe(110) surfaces. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:4102-4109. [PMID: 10004140 DOI: 10.1103/physrevb.46.4102] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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1373
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Yu X, Dluz S, Graves DT, Zhang L, Antoniades HN, Hollander W, Prusty S, Valente AJ, Schwartz CJ, Sonenshein GE. Elevated expression of monocyte chemoattractant protein 1 by vascular smooth muscle cells in hypercholesterolemic primates. Proc Natl Acad Sci U S A 1992; 89:6953-7. [PMID: 1379728 PMCID: PMC49623 DOI: 10.1073/pnas.89.15.6953] [Citation(s) in RCA: 161] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Atherosclerosis is marked by an overt inflammatory infiltrate, with enhanced recruitment of monocytes/macrophages observed in both human and experimental atherosclerosis. We previously determined that monocyte chemoattractant protein 1 (MCP-1) accounts for virtually all of the chemotactic activity produced by vascular (aortic) smooth muscle cells in culture. We now report that arteries from a primate model of atherosclerosis with dietary-induced hypercholesterolemia exhibit increased levels of MCP-1 mRNA expression in vivo, whereas their normal counterparts demonstrate minimal MCP-1 expression. Furthermore, immunohistochemistry and in situ hybridization clearly indicate that the expression of MCP-1 protein and mRNA is in the smooth muscle cells of the medial layer of the artery and in monocyte-like and smooth muscle-like cells found in the overlying intimal lesion. These studies indicate that one of the responses to dietary hypercholesterolemia is the expression of MCP-1 by vascular smooth muscle cells. This expression, when augmented with other cellular and molecular factors, could significantly contribute to the recruitment of monocytes/macrophages to the vessel wall.
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MESH Headings
- Animals
- Blotting, Northern
- Carotid Arteries/pathology
- Carotid Arteries/physiology
- Carotid Arteries/physiopathology
- Chemokine CCL2
- Chemotactic Factors/biosynthesis
- Chemotactic Factors/genetics
- Cholesterol/blood
- Cholesterol, Dietary
- Diet, Atherogenic
- Hypercholesterolemia/genetics
- Hypercholesterolemia/metabolism
- Hypercholesterolemia/pathology
- Macaca fascicularis
- Muscle, Smooth, Vascular/pathology
- Muscle, Smooth, Vascular/physiology
- Muscle, Smooth, Vascular/physiopathology
- Nucleic Acid Hybridization
- RNA/genetics
- RNA/isolation & purification
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Reference Values
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1374
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Yu X, Yuan X, Matsuda Z, Lee TH, Essex M. The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions. J Virol 1992; 66:4966-71. [PMID: 1629961 PMCID: PMC241345 DOI: 10.1128/jvi.66.8.4966-4971.1992] [Citation(s) in RCA: 260] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Accumulating evidence suggests that the matrix (MA) protein of retroviruses plays a key role in virus assembly by directing the intracellular transport and membrane association of the Gag polyprotein. In this report, we show that the MA protein of human immunodeficiency virus type 1 is also critical for the incorporation of viral Env proteins into mature virions. Several deletions introduced in the MA domain (p17) of human immunodeficiency virus type 1 Gag polyprotein did not greatly affect the synthesis and processing of the Gag polyprotein or the formation of virions. Analysis of the viral proteins revealed normal levels of Gag and Pol proteins in these mutant virions, but the Env proteins, gp120 and gp41, were hardly detectable in the mutant virions. Our data suggest that an interaction between the viral Env protein and the MA domain of the Gag polyprotein is required for the selective incorporation of Env proteins during virus assembly. Such an interaction appears to be very sensitive to conformational changes in the MA domain, as five small deletions in two separate regions of p17 equally inhibited viral Env protein incorporation. Mutant viruses were not infectious in T cells. When mutant and wild-type DNAs were cotransfected into T cells, the replication of wild-type virus was also hindered. These results suggest that the incorporation of viral Env protein is a critical step for replication of retroviruses and can be a target for the design of antiviral strategies.
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Abstract
The effects of arachidonic acid and its metabolites on gamma-aminobutyric acid (GABAA) receptor function were determined in rat cerebral cortical synaptoneurosomes. Incubation of synaptoneurosomes with phospholipase A2 decreased muscimol-induced 36Cl- uptake. Arachidonic acid, the major unsaturated fatty acid released by phospholipase A2, also inhibited muscimol-induced 36Cl uptake. Similar inhibition was obtained with other unsaturated fatty acids (docosahexaenoic, oleic) but not with saturated fatty acids (stearic, palmitic). The effect of arachidonic acid on muscimol responses was inhibited by bovine serum albumin (BSA), and BSA enhanced muscimol responses directly, indicating the generation of endogenous arachidonic acid in the synaptoneurosome preparation. The generation of endogenous arachidonic acid was also indicated by the ability of 2 inhibitors of arachidonic acid metabolism, indomethacin and nordihydroguaiaretic acid (NDGA), to inhibit muscimol-induced 36Cl uptake. We conclude that arachidonic acid probably has both direct and indirect actions on muscimol responses since both enzyme inhibitors inhibited muscimol responses but did not prevent the effect of exogenously added arachidonic acid. In additional experiments, arachidonic acid metabolites generated by cyclooxygenase, prostaglandins D2, E2 and F2 alpha, each decreased muscimol responses; prostaglandins F2 alpha was the most potent inhibitor. Since the unsaturated fatty acids and their metabolites are most susceptible to peroxidation, a generating system of superoxide radicals was tested on muscimol responses. A combination of xanthine and xanthine oxidase inhibited muscimol-induced 36Cl uptake in a concentration-dependent manner. We propose that the inhibition of GABAA neurotransmission by arachidonic acid and its metabolites can lead to increased neuronal excitability. This mechanism may play an important role in the development of neuronal damage following seizures or cerebral ischemia.
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