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R Koenig

Publications and source records attributed to R Koenig.

At least 91 records · Page 5Linked to original sources
PubMed1998

An onion isolate of tobacco rattle virus: reactivity with an antiserum to Hypochoeris mosaic virus, a putative furovirus, and molecular analysis of its RNA 2.

A tubular virus from onion was found to react with an antiserum to Hypochoeris mosaic virus (HyMV), a putative furovirus. Sequence analysis of its genomic RNAs and further serological tests, however, indicated it to be a tobravirus rather than a furovirus. The reactivity of the HyMV antiserum with several isolates of tobacco rattle virus (TRV) suggests that HyMV itself may be a tobravirus. The deduced amino acid sequences of the putative proteins encoded on RNA 2 of the onion virus isolate (ON) suggest close evolutionary relationships to the TRV isolate TCM from tulip. However, RNA 2 of the ON isolate contains a shorter RNA 1-like sequence on its 3'-end and an additional small ORF upstream of its RNA 1-like part. The sequence of its 315 5'-terminal nucleotides is more similar to that of RNA 2 of the PLB isolate from potato than to that of TCM RNA 2.

Amino Acid Sequence↗
PubMed1998

Enhanced radiosensitivity in experimental tumours following erythropoietin treatment of chemotherapy-induced anaemia.

The radiosensitivity of solid tumours in anaemic rats treated with recombinant human erythropoietin (rhEPO, epoetin beta) was studied. Anaemia was induced by a single dose of carboplatin (45 mg kg(-1) i.v.), resulting in a reduction in the haemoglobin concentration by 30%. In a second group, the development of anaemia was prevented by rhEPO (1000 IU kg(-1)) administered s.c. three times per week starting 6 days before the carboplatin application. Three days after carboplatin treatment, DS-sarcomas were implanted subcutaneously onto the hind foot dorsum. Neither carboplatin nor rhEPO treatment influenced tumour growth rate. Five days after implantation, tumours were irradiated with a single non-curative dose (10 Gy), resulting in a growth delay with a subsequent regrowth of the tumours. In the rhEPO-treated group, the growth delay lasted significantly longer (9.5 days vs. 4.5 days) and the regrowth was slower (6.0 days vs. 4.1 days) compared with the anaemic group. These data suggest that the correction of chemotherapy-induced anaemia by rhEPO (epoetin beta) treatment increases tumour radiosensitivity, presumably as a result of an improved oxygen supply to tumour tissue.

Anemia↗
PubMed1998

Genome properties of beet virus Q, a new furo-like virus from sugarbeet, determined from unpurified virus.

Based solely on the information that beet virus Q (BVQ) contains tubular particles, the entire nucleotide sequence of its tripartite genome was determined from unpurified virus in ca. 40 ml crude sap from locally infected Chenopodium quinoa. A starting sequence for RNA 1 was generated using primers corresponding to highly conserved helicase domains in the respective RNAs of furo-, pomo-, peclu-, hordei- and tobraviruses, and was extended by a walking random-primed cDNA approach. The similarity of the 3' ends of furoviral RNAs allowed starting sequences for BVQ RNAs 2 and 3 to be obtained once the 3' end of RNA 1 was known. BVQ RNA 1 encodes a protein with a methyltransferase-like, a variable and a helicase-like region, and for a readthrough protein which, in addition, contains an RNA-dependent RNA polymerase region. RNA 2 carries the coat protein gene, a coat protein read-through protein gene and two additional ORFs which may have arisen by deletions from an originally larger readthrough domain. RNA 3 carries a triple gene block resembling that of several other rod-shaped viruses. The 5' UTRs of the three RNAs have the potential to form a series of hairpins with C-A and C-C mismatches resembling those found in tymoviral RNAs. The 3' ends can be folded into tRNA-like structures which are preceded by a long hairpin-like structure and an upstream pseudoknot domain. BVQ belongs to the recently proposed genus Pomovirus; it shows evolutionary relationships to furoviruses in sensu stricto, peclu-, hordei-, tobra-, tymo-, tobamo-, carla- and potexviruses.

Amino Acid Sequence↗
PubMed1997

Single-chain Fv fusion proteins suitable as coating and detecting reagents in a double antibody sandwich enzyme-linked immunosorbent assay.

A recombinant enzyme-linked immunosorbent assay (ELISA) system, entirely based on antibody fragments, is described here as an attractive alternative to assays using polyclonal antisera or monoclonal antibodies. Two expression vectors have been developed for cloning and production of single-chain Fv (scFv) fusion proteins suitable as coating and detecting reagents, respectively, in a highly sensitive double antibody sandwich ELISA. The coating reagent is produced from the vector pZIP1, as a bivalent miniantibody with a leucine zipper for dimerization. The detection reagent is a fusion protein, in which a modified Escherichia coli alkaline phosphatase with increased specific activity is attached to the carboxy-terminus of the scFv. This conjugate is produced using pDAP2/S as cloning and expression vector. Optimized bacteria expression and simple one-step purification by hexahistidine tag-mediated metal chelate affinity chromatography yielded milligrams of ELISA reagent per liter of bacterial culture in both cases. A double antibody sandwich ELISA for the detection of beet necrotic yellow vein virus, the causal agent of sugarbeet rhizomania, was developed using fusion proteins obtained by means of pZIP1 and pDAP2/S. The plant pathogen was detected with a sensitivity higher than that reached in a conventional ELISA employing polyclonal antisera. Both plasmid vectors are compatible to phage display vectors such as pHEN1, pCOCK, and the pCANTAB series, allowing simple subcloning after isolation of scFv from phage display libraries. It is therefore easy to develop and produce an ELISA entirely by using bacterial recombination and expression techniques.

Alkaline Phosphatase↗
PubMed1997

Nicotiana benthamiana plants expressing beet necrotic yellow vein virus (BNYVV) coat protein-specific scFv are partially protected against the establishment of the virus in the early stages of infection and its pathogenic effects in the late stages of infection.

Transgenic plants of Nicotiana benthamiana expressing single chain antibody fragments (scFv) specific for the coat protein of beet necrotic yellow vein virus (BNYVV) and non-expressing control plants were inoculated with BNYVV mechanically and by means of the vector Polymyxa betae. The scFv were presumably expressed in the endoplasmic reticulum (ER). The average time needed for infections to become detectable was longer in the scFv-expressing plants than in the non-expressing control plants. In addition, the scFv-expressing plants were partially protected against the pathogenic effects exerted by the virus on N. benthamiana plants in the late stages of infection.

Antibodies, Viral↗
PubMed1997

Beet soil-borne virus RNA 1: genetic analysis enabled by a starting sequence generated with primers to highly conserved helicase-encoding domains.

The complete sequence of the 5834 nucleotides of RNA 1 of beet soil-borne furovirus (BSBV, Ahlum isolate) was determined using a PCR product obtained with primers to highly conserved coding regions for helicase-like proteins in RNA 1 of furo-, hordei- and tobraviruses as a starting sequence. Unknown parts of the sequence upstream and downstream of this starting sequence were amplified by means of RT-PCR techniques using combinations of specific and random primers. BSBV RNA 1 contains one large ORF for a readthrough protein with a molecular mass of 204 kDa (204K protein) which is interrupted internally by a UAA stop codon terminating the coding region for a protein of 145 kDa (145K protein). The N- and C-terminal parts of the 145K protein and the readthrough domain of the 204K protein contain methyltransferase, helicase and RNA-dependent RNA polymerase motifs, respectively. Unlike other furo- and tobraviruses BSBV contains no further genes on its RNA 1.

Amino Acid Sequence↗
PubMed1997

Beet soil-borne virus RNA 2: similarities and dissimilarities to the coat protein gene-carrying RNAs of other furoviruses.

The complete sequence of the 3454 nt of RNA 2 of the Ahlum isolate of beet soil-borne furovirus (BSBV) has been determined starting with two short stretches of cloned cDNA. Unknown parts of the sequence were amplified by means of RT-PCR techniques using combinations of specific and random primers. BSBV RNA 2 is more similar in its genetic organization to potato mop top virus (PMTV) RNA 3 than to any other furoviral RNA, although it is more than 1100 nt longer. Its 3'-end, unlike that of PMTV RNA 3, has the potential to fold into a tRNA-like structure. It contains one large open reading frame for a readthrough protein with a molecular mass of 104 kDa (104K protein) which is interrupted internally by an amber stop codon terminating the coding region for a protein of 19 kDa (19K), most likely the viral coat protein (CP). The readthrough domain of the 104K protein is much larger than that of PMTV, but the N- and C-proximal portions of these domains are similar for the two viruses. No serological relationships were found between the particles of the two viruses, although more than 50% of the amino acid sequences of the putative CPs are identical.

Amino Acid Sequence↗
PubMed1997

Detection and characterization of a distinct type of beet necrotic yellow vein virus RNA 5 in a sugarbeet growing area in Europe.

A fifth beet necrotic yellow vein virus (BNYVV) RNA species has been detected in Europe in sugarbeet infected with P-type BNYVV. Very little sequence variation was found between two European sources of this RNA 5*, but considerable differences were detected between these two European sources on the one hand and the four Japanese sources recently analysed by Kiguchi et al. on the other. The BNYVV RNA 5-encoded 26 K proteins share a stretch of six amino acids (FRGPGN) with the BNYVV RNA 3-encoded 25 K protein which may be of interest in view of the reported interactions between the two RNAs in pathogenicity.

Amino Acid Sequence↗