Dorit Landstein - Academia.edu (original) (raw)

Papers by Dorit Landstein

... FURUTA Masakszu; Research Institute for Advanced Science and Technology, University of Osaka ... more ... FURUTA Masakszu; Research Institute for Advanced Science and Technology, University of Osaka Prefecture. SCHRADER John O. University of Nebraska. SHRADER Holly S. University of Nebraska. KOKJOHN Tyler; University of Nebraska. ...

AGRIS record. Record number, US9602399. Titles, Is the inhibitory effect of the herbicide sulfome... more AGRIS record. Record number, US9602399. Titles, Is the inhibitory effect of the herbicide sulfometuron methyl due to 2-ketobutyrate accumulation? Personal Authors, Epelbaum, S. (Ben-Gurion University, Beer-Sheva, Israel.),Landstein ...

The bacteriophage T4 denV gene encodes a well-characterized DNA repair enzyme involved in pyrimid... more The bacteriophage T4 denV gene encodes a well-characterized DNA repair enzyme involved in pyrimidine photodimer excision. We have discovered the first homologs of the denV gene in chlorella viruses, which are common in fresh water. This gene functions in vivo and also when cloned in Escherichia coli. Photodamaged virus DNA can also be photoreactivated by the host chlorella. Since the chlorella viruses are continually exposed to solar radiation in their native environments, two separate DNA repair systems, one that functions in the dark and one that functions in the light, significantly enhance their survival.

Journal of Radiation Research, Dec 1, 1996

Journal of immunology (Baltimore, Md. : 1950), Jan 22, 2015

We have previously shown that naturally occurring as well as acquired Abs against the Mycobacteri... more We have previously shown that naturally occurring as well as acquired Abs against the Mycobacterium tuberculosis heat shock protein (HSP)65 protect against the induction of murine autoimmune inflammatory arthritis. In the present work, we have studied the anti-inflammatory effect of prozumab, a humanized anti-HSP mAb in murine inflammatory arthritis and colitis, and its effects on cytokine secretion. Prozumab was shown to bind to HSP60, the highly conserved mammalian homolog of the bacterial protein, and it was found to be effective in protecting and suppressing autoimmune arthritis in the models of adjuvant arthritis and collagen-induced arthritis in rats and mice, respectively, as well as in acute hapten-mediated colitis and chronic, spontaneous colitis models. Mechanistically, prozumab induces IL-10 secretion from naive human PBMCs and suppresses the secretion of IFN-γ and IL-6 from anti-CD3-activated human PBMCs. These findings make prozumab a promising potential drug for treati...

Virology, Jan 25, 1998

DNA sequence analysis of the 330-kb Chlorella virus PBCV-1 genome unexpectedly revealed several o... more DNA sequence analysis of the 330-kb Chlorella virus PBCV-1 genome unexpectedly revealed several open reading frames which encode proteins that are homologous to sugar-manipulating enzymes including glutamine:fructose-6-phosphate amidotransferase (GFAT), UDP-glucose dehydrogenase (UDP-GlcDH), and hyaluronan synthase (HAS). PBCV-1 genes encoding the putative GFAT and UDP-GlcDH enzymes were expressed in Escherichia coli, and both recombinant proteins have the predicted enzyme activity in cell free extracts. These same two genes are transcribed early in PBCV-1 infection, and both genes are widespread among the Chlorella viruses. The products of the reactions catalyzed by these two enzymes are precursors in the biosynthesis of hyaluronan polysaccharide. Previous experiments established that, like the GFAT and UDP-GlcDH genes, the HAS gene is transcribed early and encodes a functional enzyme (DeAngelis, P. L., Jing. W., Graves, M. V., Burbank, D. E., and Van Etten, J. L. (1997) Science 27...

Applied and environmental microbiology, 1997

Virology, 1996

PBCV-1 belongs to a family of large viruses that replicate in the exsymbiont green algae Chlorell... more PBCV-1 belongs to a family of large viruses that replicate in the exsymbiont green algae Chlorella strain NC64A. The viral, 330-kb DNA genome encodes a relatively large number of functionally active proteins including restriction and modification enzymes, DNA polymerase, glycosylation, and cell wall degrading enzymes. Sequencing of the viral DNA, now in progress, revealed many major open reading frames (ORF), which resemble known genes in sequence data bases and which have not previously been found in viral genomes. Here we report on the identification and characterization of one such gene, aspartate transcarbamylase (ATCase), an enzyme that catalyzes the committing step in the de novo biosynthetic pathway of pyrimidines. The cloned gene is highly homologous to a variety of plant ATCases and includes the typical ATCase catalytic motif. When cloned into the pGEX-2T expression vector, a fusion protein with ATCase activity could be demonstrated and distinguished from the host ATCase activity. The viral enzyme is expressed early and transiently in the infection. To our knowledge, this is the first virus known to encode and express its own de novo nucleotide precursors' synthetic enzymes. ᭧

Virology, 1995

Four spontaneously derived, antigenic variants of chlorella virus PBCV-1 contained 27-to 37-kb de... more Four spontaneously derived, antigenic variants of chlorella virus PBCV-1 contained 27-to 37-kb deletions in the left end of the 330-kb genome. Two of the mutants, which were serologically identical, had deletions that began from map position 4.9 or 16 and ended at position 42.2 kb. In total, the two deleted regions encoded 28 putative functional open reading frames (ORFs); these deletions probably arose from homologous recombination. The other two mutants, which were serologically identical but distinct from the first two mutants, lacked the entire left terminal 37 kb of the PBCV-1 genome, including an identical 2.2-kb inverted terminal repeat region present at both ends of the wild-type genome. The deleted left end region was replaced by the transposition of an inverted 7.7-or 18.5-kb copy of the right end of the PBCV-1 genome. The region deleted in these two viruses encoded 26 single-copy ORFs, of which 23 were common to those deleted in the first two mutant viruses. The junctions of the deletions/transpositions probably arose from nonhomologous recombination. Taken together, the results indicate that 40.1 kb of single-copy DNA encoding 31 ORFs at the left end of the genome are unnecessary for PBCV-1 replication in Chlorella strain NC64A in the laboratory. The results also indicate that the size of the inverted terminal repeat region in this virus can be highly variable and that the PBCV-1 DNA packaging process tolerates large changes in genome size. ᭧

Planta, 1995

Abbreviations: AHAS = acetohydroxy acid synthase; BCAA = branched-chain amino acids; IM = imidazo... more Abbreviations: AHAS = acetohydroxy acid synthase; BCAA = branched-chain amino acids; IM = imidazolinone; ctKB, ct-ketobutyrate; SMM = sulfometuron methyl; SU = sulfonyl urea Correspondence to: D.M. Chipman; FAX: 972 note that an important difference between the effect of SMM and that observed with externally added 0tKB is that the ratio between intracellular QtKB and 0t-ketoisovalerate is expected to be high in the first case, but not necessarily in the second.

Planta, 1993

The properties of acetohydroxy acid synthase (AHAS, EC 4.1.3.18) from wild-type Chlorella emerson... more The properties of acetohydroxy acid synthase (AHAS, EC 4.1.3.18) from wild-type Chlorella emersonii (var. Emersonii, CCAP-211/lln)and two spontaneous sulfometuron methyl (SMM)-resistant mutants were examined. The AHAS from both mutants was resistant to SMM and cross-resistant to imazapyr (IM) and the triazolopyrimidine sulfonanilide herbicide XRD-498 (TP). The more-SMM-resistant mutant had AHAS with altered catalytic parameters (Km, specificity), but unchanged sensitivity to the feedback inhibitors valine and leucine. The second mutant enzyme was less sensitive to the feedback inhibitors, but had otherwise unchanged kinetic parameters. Inhibition-competition experiments indicated that the three herbicides (SMM, IM, TP) bind in a mutually exclusive manner, but that valine can bind simultaneously with SMM or TP. The three herbicide classes apparently bind to closely overlapping sites. We suggest that the results with C. emersonii and other organisms can all be explained if there are separate binding sites for herbicides, feedback inhibitors and substrates.

PLANT PHYSIOLOGY, 1990

Acetohydroxyacid synthase (AHAS) activity was studied in the green unicellular alga Chlorella eme... more Acetohydroxyacid synthase (AHAS) activity was studied in the green unicellular alga Chlorella emersonii. This activity and its regulation was compared in the algae grown autotrophically and heterotrophically on glucose in the dark. No evidence for the existence of more than one enzyme was found. The activity in crude extracts from either heterotrophically or autotrophically grown cells showed a Km for pyruvate of 9 millimolar, a 22-fold preference for 2-ketobutyrate over pyruvate as the second substrate, 50% inhibition by 0.5 millimolar valine, and 50% inhibition by 0.3 micromolar sulfometuron methyl (SMM). Spontaneous mu-

Journal of Virology, 2006

Passive immunotherapy is potentially effective in preventing reinfection of liver grafts in hepat... more Passive immunotherapy is potentially effective in preventing reinfection of liver grafts in hepatitis C virus (HCV)-associated liver transplant patients. A combination of monoclonal antibodies directed against different epitopes may be advantageous against a highly mutating virus such as HCV. Two human monoclonal antibodies (HumAbs) against the E2 envelope protein of HCV were developed and tested for the ability to neutralize the virus and prevent human liver infection. These antibodies, designated HCV-AB 68 and HCV-AB 65, recognize different conformational epitopes on E2. They were characterized in vitro biochemically and functionally. Both HumAbs are immunoglobulin G1 and have affinity constants to recombinant E2 constructs in the range of 10 ؊10 M. They are able to immunoprecipitate HCV particles from infected patients' sera from diverse genotypes and to stain HCV-infected human liver tissue. Both antibodies can fix complement and form immune complexes, but they do not activate complement-dependent or antibody-dependent cytotoxicity. Upon complement fixation, the monoclonal antibodies induce phagocytosis of the immune complexes by neutrophils, suggesting that the mechanism of viral clearance includes endocytosis. In vivo, in the HCV-Trimera model, both HumAbs were capable of inhibiting HCV infection of human liver fragments and of reducing the mean viral load in HCV-positive animals. The demonstrated neutralizing activities of HCV-AB 68 and HCV-AB 65 suggest that they have the potential to prevent reinfection in liver transplant patients and to serve as prophylactic treatment in postexposure events.

Journal of Hepatology, 2003

Journal of Clinical Virology, 2006

Abstracts, 12th ISHVLD and morbidity, medical follow-up and treatment status. Together these stud... more Abstracts, 12th ISHVLD and morbidity, medical follow-up and treatment status. Together these studies have contributed to our understanding of the time course of evolution to resolved versus chronic HCV infection, and to identification of viral and host genetic and immunological factors correlating with control of viremia and clinical disease progression.