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Biomedical subjects

K W Buck

Publications and source records attributed to K W Buck.

At least 73 records · Page 4Linked to original sources
PubMed1978

Semi-conservative transcription in particles of a double-stranded RNA mycovirus.

During transcription in vitro catalysed by the virion RNA polymerase of Aspergillus foetidus virus AfV-S in the presence of tritiated UTP, the virus double-stranded RNA becomes labelled in one strand, which has the same sequence as the single-stranded RNA transcripts produced. Most of the label incorporated into double-stranded RNA could be chased into single stranded RNA by further reaction with excess unlabelled nucleoside triphosphates. In reactions containing tritiated UTP the single-stranded RNA transcripts released after the first round of transcription were unlabelled. It is concluded that transcription in virions of AfV-S occurs by displacement of one of the strands of double-stranded RNA by the RNA strand being newly synthesised i.e. the reaction is semi-conservative with respect to double-stranded RNA.

Aspergillus↗
PubMed1977

Comparison of the biophysical and biochemical properties of Penicillium cyaneo-fulvum virus and Penicillium chrysogenum virus.

The biophysical and biochemical properties of Penicillium cyaneo-fulvum virus (Pc-fV) and Penicillium chrysogenum virus (PcV) have been compared. In sucrose density gradient sedimentation, purified virus preparations gave one major component, L, and three minor components E1, E2 and H with sedimentation coefficients of 145S, 80S, 102S and 172S respectively in each case. E1, E2 were shown to be empty particles. Pc-fV L particles contained only double-stranded RNA, which separated in polyacrylamide gel electrophoresis into four components with mol. wt. 2-21 X 10(6), 2-08 X 10(6), 1-98 X 10(6) and 1-93 X 10(6). PcV L particles gave three double-stranded RNA components, which were indistinguishable in polyacrylamide gel electrophoresis from the larger three RNA components of Pc-fV. In both viruses each RNA component was separately encapsidated. In both viruses H particles gave rise to the same double-stranded RNA components as their L particles, but contained, in addition, small amounts of single-stranded RNA. Pc-fV and PcV have been shown to consist of isometric particles of the same size and to be serologically related, and the amino acid compositions of their capsid polypeptides were found to be very similar. The capsid polypeptides of the two viruses were examined by SDS-polyacrylamide gel electrophoresis. In each case E2, L and H particles gave one major polypeptide gamma1, with mol. wt. 130000, whereas E1 particles contained one major polypeptide gamma2 with mol. wt. 115000. The mol. wt. of L particles, determined from sedimentation and diffusion coefficients, was 9-8 X 10(6) for both Pc-fV and PcV. The capsid of the L particles of each virus was estimated to contain 60 molecules of polypeptide gamma1.

Amino Acids↗
PubMed1977

Molecular weight of double-stranded RNA: a re-examination of Aspergillus foetidus virus S RNA components.

The mol. wt of the three double-stranded RNA (ds-RNA) components of Aspergillus foetidus virus S have been re-determined by using polyacrylamide gel electrophoresis (a) of native ds-RNA with ds-RNA standards and (b) of denatured ds-RNA with single-stranded RNA standards. Good agreement between the two methods and confirmation that the relationship between log mol. wt. and electrophoretic mobility of ds-RNA is not linear were obtained. The new mol. wt. values (4-0 to 4-2 x 10(6); 2-5 to 2-7 x 10(6) and 0-26 to 0-28 x 10(6), resepectively) are significantly higher than those determined previously by linear extrapolation from reovirus ds-RNA standards.

Aspergillus↗
PubMed1975

Replication of double-stranded RNA in particles of Penicillium stoloniferum virus S.

RNA polymerase activity was assayed in different particle classes of Penicillium stoloniferum virus S. RNA polymerase activity was found to be associated with H particles, which contain double-stranded RNA and single-stranded RNA, but not with L particles, which contain only double-stranded RNA and not with M particles, which contain only single-stranded RNA. In H particles the reaction occurred with the formation of one new molecule of double-stranded RNA (or two complementary single strands of RNA) per virus particle and the production of product particles (P particles), which contained two molecules of double-stranded RNA (or its equivalent). This RNA polymerase is therefore a replicase, which catalyses the synthesis of the two complementary strands of double-stranded RNA in a single virus particle. This is the first report of this type of RNA polymerase system.

Centrifugation, Density Gradient↗
PubMed1975

Biophysical and biochemical properties of two viruses isolated from Aspergillus foetidus.

Aspergillus foetidus virus S (AfV-S) and A. foetidus virus F(AfV-F) have been shown to be serologically unrelated. Amino acid compositions of the two virus capsids are compared and their capsid polypeptides have been examined by SDS-polyacrylamide gel electrophoresis. AfV-F contained one major (phi3) and two minor (phi1 and phi2) polypeptides with mol. wt. 87000, 125000 and 100000, while AfV-S contained one major (sigma1) and one minor (sigma2) polypeptide with mol. wt. 83000 and 78000 respectively. Evidence is presented that sigma2 may be derived from sigma1 polypeptide by proteolytic degradation in vitro. The mol. wt. of AfV-F4 and AfV-S1a particles were found from sedimentation and diffusion coefficients to be 13 I times 10-6 and 12 4 times 10-6 respectively. AfV-F capsid was estimated to contain 120 molecules of polypeptide phi3 and one molecule each of polypeptides phi1 and phi2, while AfV-S capsid was estimated to contain 120 molecules of polypeptide phi1. It has been shown that SIa and S-2a particles each contain a molecule of double-stranded RNA with mol. wt. 2 24 times 10-6 (RNA-224) and 2 76 times 10-6 (RNA-276) respectively, whereas S-Ib and S-2b particles each contain a molecule of RNA-224 and RNA-276 respectively, together with an additional molecule of double-stranded RNA of mol. wt. 0 I times 10-6. Evidence is presented that S4 particles contain two molecules of RNA-224. S3 particles gave only RNA-224 on extraction, but contain the equivalent of 11/2 molecules of RNA-224; the nature of these particles and other possible virus replicative intermediates is discussed. Double-stranded RNA of mol. wt. I 24 times 10-6 was derived from a newly described particle class, Fo.

Amino Acids↗
PubMed1971

The composition of the cell wall of Fusicoccum amygdali.

1. The cell wall of Fusicoccum amygdali consisted of polysaccharides (85%), protein (4-6%), lipid (5%) and phosphorus (0.1%). 2. The main carbohydrate constituent was d-glucose; smaller amounts of d-glucosamine, d-galactose, d-mannose, l-rhamnose, xylose and arabinose were also identified, and 16 common amino acids were detected. 3. Chitin, which accounted for most of the cell-wall glucosamine, was isolated in an undegraded form by an enzymic method. Chitosan was not detected, but traces of glucosamine were found in alkali-soluble and water-soluble fractions. 4. Cell walls were stained dark blue by iodine and were attacked by alpha-amylase, with liberation of glucose, maltose and maltotriose, indicating the existence of chains of alpha-(1-->4)-linked glucopyranose residues. 5. Glucose and gentiobiose were liberated from cell walls by the action of an exo-beta-(1-->3)-glucanase, giving evidence for both beta-(1-->3)- and beta-(1-->6)-glucopyranose linkages. 6. Incubation of cell walls with Helix pomatia digestive enzymes released glucose, N-acetyl-d-glucosamine and a non-diffusible fraction, containing most of the cell-wall galactose, mannose and rhamnose. Part of this fraction was released by incubating cell walls with Pronase; acid hydrolysis yielded galactose 6-phosphate and small amounts of mannose 6-phosphate and glucose 6-phosphate as well as other materials. Extracellular polysaccharides of a similar nature were isolated and may be formed by the action of lytic enzymes on the cell wall. 7. About 30% of the cell wall was resistant to the action of the H. pomatia digestive enzymes; the resistant fraction was shown to be a predominantly alpha-(1-->3)-glucan. 8. Fractionation of the cell-wall complex with 1m-sodium hydroxide gave three principal glucan fractions: fraction BB had [alpha](D) +236 degrees (in 1m-sodium hydroxide) and showed two components on sedimentation analysis; fraction AA(2) had [alpha](D) -71 degrees (in 1m-sodium hydroxide) and contained predominantly beta-linkages; fraction AA(1) had [alpha](D) +40 degrees (in 1m-sodium hydroxide) and may contain both alpha- and beta-linkages.

Amino Acids↗
PubMed1971

Characterization of two cell-wall polysaccharides from Fusicoccum amygdali.

1. The nature of two polysaccharides (s(0) (20) values 6S and 2S respectively in 1m-sodium hydroxide), comprising a fragment (fraction BB, [alpha](D) +236 degrees in 1m-sodium hydroxide), previously isolated from cell walls of Fusicoccum amygdali, has been investigated. 2. Both the major (2S) and minor (6S) components were affected by incubation with alpha-amylase. The 6S polysaccharide was also attacked by exo-beta-(1-->3)-glucanase, which is evidence that it contained both alpha-(1-->4)- and beta-(1-->3)-glucopyranose linkages. By fractionation of the products of alpha-amylase-treated fraction BB it was possible to obtain a water-insoluble polysaccharide, fraction P ([alpha](D) +290 degrees in 1m-sodium hydroxide, 67% of fraction BB) and a water-soluble polysaccharide, fraction Q ([alpha](D) +16 degrees in 1m-sodium hydroxide, 11% of fraction BB), both of which sedimented as single boundaries with s(0) (20) values (in 1m-sodium hydroxide) of 1.7S and 4.6S respectively. 3. Evidence from periodate oxidation, methylation analysis, i.r. spectroscopy and partial acid hydrolysis showed that fraction P consisted of linear chains of alpha-(1-->3)-glucopyranose units with blocks of one or two alpha-(1-->4)-glucopyranose units interspersed at intervals along the main chain. The 2S polysaccharide, from which fraction P is derived, evidently also contains longer blocks of alpha-(1-->4)-glucopyranose units, that are susceptible to alpha-amylase action. 4. Fraction Q consisted of glucose (88%) with small amounts of galactose, mannose and rhamnose. Evidence from digestion with exo- and endo-beta-(1-->3)-glucanases, periodate oxidation and methylation analysis suggests that fraction Q consists of a branched galactomannorhamnan core, to which is attached a beta-(1-->3)-, beta-(1-->6)-glucan. In the cell wall, chains of alpha-(1-->4)-linked glucopyranose units are linked to fraction Q to form the 6S component of fraction BB.

Amylases↗