Relationships Between Tobacco Mosaic Virus and the Non-Virus Proteins

Commoner, Barry; Rodenberg, Sidney D.

doi:10.1085/jgp.38.4.475

Cited by 20 publications

(5 citation statements)

References 7 publications

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“…As found by Commoner & Rodenberg (1955), infective virus and sedimentable antigen occur in inoculated leaves before any unsedimented antigen is detectable. This does not necessarily mean that the virus is produced first; if sedimentable and unsedimented antigen were being produced simultaneously in the ratio in which they occur later, the unsedimented antigen would not be detected by our methods until the precipitation end-point of sap exceeds l / l O O .…”

Section: The Infectivity Of Preparationssupporting

confidence: 52%

“…The measurement of antigen content by precipitation tests Commoner & Rodenberg (1955) commented on the fact, for which they said they could offer no explanation, that preparations of the fraction they called B 8 yielded smaller precipitates with its homologous antiserum than infective preparations of TMV yielded with this serum. The explanation probably lies in the different average particle size of the antigens in the two types of preparation, for although they described their B 8 as a polymerized protein, their method of aggregation (exposure to pH 5) would probably still leave many particles smaller than those in normal preparations of TMV purified by the usual method.…”

Section: Resultsmentioning

confidence: 99%

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Observations on the Anomalous Proteins Occurring in Extracts from Plants Infected with Strains of Tobacco Mosaic Virus

Bawden

Pirie

1956

Journal of General Microbiology

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SUMMARY: When extracts from plants infected with various strains of tobacco mosaic virus were ultracentrifuged, the non-infective supernatant fluids still contained 0.5-5 yo of the protein serologically related to the viruses. The small, mostly spherical, particles aggregated to form short rods as the antigen was progressively purified by precipitation with acid or salts. It formed long rods when heated in pH 5-5 buffer or when incubated with trypsin. *4s the particles increased in length, their serological behaviour in precipitation tests changed from ' somatic' to 'flagellar' type.Purified preparations of the unsedimented antigen from plants infected with either of two virus strains contained 0.1-0.2~0 phosphorus, seemingly in the form of a ribose nucleic acid. No evidence was obtained that the preparations were mixtures containing some particles with the 0-5 yo phosphorus characteristic of infective virus and some particles of protein free from nucleic acid.One virus strain produced a higher ratio than the others of unsedimented to sedirnented antigen. The amount of unsedimented antigen was correlated with the total content of anomalous protein when the protein was increasing rapidly, but later it fluctuated unpredictably. No conditions were found that consistently favoured its accumulation, but when plants systemically infected with the type strain were kept a t 36", the total amount of antigen decreased, while the amount unsedimented sometimes increased.The proportion of the total antigen now obtained as poorly infective nucleoprotein is much less than 10 years ago, when a third of it sedimented in the ultracentrifuge but failed to compact into a pellet. Now the uncompacted sediment, with all the host plants and virus strains used, contains only a trivial part of the total antigen.The virus released into sap when leaves are minced is, weight for weight, more infective than the virus that remains in the leaf residues until it is released by fine grinding.The early work on the anomalous protein contained in virus-infected plants was done primarily to identify material that could be related to the viruses themselves, and its main aim was to make preparations with the maximum infectivity and the minimum of different components. Little attention was given to non-infective material, and the emphasis laid on the homogeneity of purified preparations served only to strengthen the general assumption that viruses multiply by the replication of an infecting particle to give a result that is uniform except for occasional variants regarded as equivalent to mutations. When we (Bawden & Pirie, 1945a, b ) found that plants infected with the Rothamsted tobacco necrosis virus or with tobacco mosaic virus (TMV) contained more than one type of anomalous protein, we questioned the validity of this assumption, and have since argued (Bawden & Pirie, 1950a, b, 1952, 1953 that infection is more usefully regarded as a change in the protein metabolism

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Section: The Infectivity Of Preparationssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Observations on the Anomalous Proteins Occurring in Extracts from Plants Infected with Strains of Tobacco Mosaic Virus

Bawden

Pirie

1956

Journal of General Microbiology

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“…However, it has also been found that TMV can easily shed a small proportion of its protein (Kleczkowski, 1957) and so X-protein may come from virus particles and not be their precursor. That it does not come from previously formed virus particles, at least not entirely, is suggested by the results of experiments with 15N (Delwiche, Newmark, Takahashi & Ng, 1955; Commoner & Rodenberg, 1955) and 14C (van Rysselberge & Jeener, 1957) within TMV infected plants. Both isotopes were incorporated into X-protein and into TMV at about the same rates, and so X-protein and TMV were probably synthesized simultaneously, or nearly so.…”

Section: X-proteinmentioning

confidence: 97%

Protein of Tobacco Mosaic Virus

Kleczkowski

1963

Biological Reviews

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Summary A typical infective rod‐shaped particle of tobacco mosaic virus (TMV) is composed of ribonucleic acid, of molecular weight about 2,000,000 and about 2200 helically arranged protein sub‐units, each with a molecular weight of about 18,000. The sub‐unit is made of a single chain of 158 amino‐acid residues of known sequence. The thread of the nucleic acid is sandwiched between protein sub‐units and follows their helical array about the long axis of the particle. The virus is easily degraded, and the protein separated from the nucleic acid, by alkali. The protein thus obtained, called A‐protein, has particles of molecular weight about 100,000, composed of 6 protein sub‐units. When the pH is lowered to below 6, particles of the A‐protein polymerize. This is comparable to crystallization, with protein sub‐units fitting into a regular pattern as in the original virus particle. Infectivity is a function of the virus nucleic acid and the nucleic acid free from protein is infective. The only known biological function of the protein is to stabilize the nucleic acid and protect it from ribonuclease and some other inactivating agents. A remarkable property of the A‐protein and of free virus‐nucleic acid is their ability to recombine to form ‘reconstituted’ virus, which is similar to the original virus. Sap from plants infected with TMV contains not only the virus, but also free protein, called X‐protein, which is similar to and may be identical with the A‐protein. It also combines with virus‐nucleic acid to form virus‐like infective particles. X‐protein may be surplus virus protein not incorporated into virus particles, but some may come from virus particles, which readily shed a small proportion of their protein. Walls of protein sub‐units seem to differ in various physico‐chemical aspects, such as electrokinetic potential at the surface and susceptibility to proteolytic enzymes as trypsin or papain. Polymerization, which conceals some of these walls, alters electro‐phoretic mobility and isoelectric point, and confers resistance to proteolytic enzymes. Serological behaviour of TMV is entirely a function of its protein. Whether the protein sub‐units are all antigenically identical is uncertain. The fact that A‐protein can form several precipitation bands with antiserum to TMV in the gel‐diffusion precipitin test suggests that there are several antigenically different kinds of protein sub‐unit, but is not conclusive, for a homogeneous antigen can sometimes form several bands. Other facts, however, point to the conclusion that there are at least two, and possibly more, antigenically different kinds of protein sub‐units. If all the sub‐units have the same amino‐acid composition and sequence, but differ antigenically, this presumably means that the polypeptide chains may be folded differently. A‐protein (and X‐protein) may have an antigenic determinant that becomes concealed when the protein is polymerized. Some pronounced differences in serological behaviour between TMV and polymerized A‐protein (or X‐protein), on the one...

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“…Aliquots of the fractions were then precipitated with 0.01 ml. of anti-TMV rabbit serum, according to a procedure described elsewhere (7). The relative antigen content of each tube was then determined from the quotient, precipitin value/protein concentration of tube.…”

Section: The Non-virus Proteins Unique To Infected Leafmentioning

confidence: 99%

The Non-Virus Proteins Associated With Tobacco Mosaic Virus

Commoner¹,

Yamada²

1955

The Journal of General Physiology

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1. Exhaustive fractionation of leaves from tobacco plants systemically infected with TMV has led to the isolation of two non-virus proteins, B3 and B6, and the detection of a third, A4, which do not occur in comparable uninfected plants. 2. Components B3 and B6 have been found consistently in a series of ten extracts from plants grown over an 18 month period in all seasons of the year. It is concluded that these components are as characteristic of the infected plant as TMV itself. 3. As they occur in the initial extracts, the non-virus proteins are of low molecular weight (S20 ca. 3). On treatment, each component tends to form a high molecular weight polymer with an electrophoretic mobility considerably greater than that of the starting material. The high molecular weight derivatives of A4, B3, and B6 have been designated A8, B8, and B7 respectively. There is no evidence that these high molecular weight components occur as such in the infected leaf. 4. The non-virus proteins are free of nucleic acid and are not infectious. They cross-react immunochemically with TMV. 5. Compared with TMV content, the amounts of the non-virus proteins found in infected leaf are relatively small, falling in the range of 10 to 150 micrograms per gm. of tissue.

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Relationships Between Tobacco Mosaic Virus and the Non-Virus Proteins

Cited by 20 publications

References 7 publications

Observations on the Anomalous Proteins Occurring in Extracts from Plants Infected with Strains of Tobacco Mosaic Virus

Observations on the Anomalous Proteins Occurring in Extracts from Plants Infected with Strains of Tobacco Mosaic Virus

Protein of Tobacco Mosaic Virus

The Non-Virus Proteins Associated With Tobacco Mosaic Virus

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