Tobacco mosaic virus—A calcium-magnesium coordination complex

Loring, Hubert S.; Fujimoto, Yasuo; Tu, Anthony T.

doi:10.1016/0042-6822(62)90199-x

Cited by 30 publications

(10 citation statements)

References 16 publications

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“…The isoelectric point of the virus is at about pH 3.2 [68], but, from osmotic pressure data, the net charge on TMV is nearly zero at neutral pH, and removal of Ca2+ makes it substantially negative at this pH [69]. TMV was found to bind approximately two Ca2 + ions per protein subunit with a high affinity and considerable selectivity over other cations [70], while it was also found that about twenty molecules of a polyamine bind to each virus particle [71]. Clearly the net charge on particles in any preparation of TMV will be markedly dependent upon the conditions used both for its isolation and for any subsequent treatment.…”

Section: Other Injormationmentioning

confidence: 99%

A Prediction of the Structure of Tobacco-Mosaic-Virus Protein

Durham

Butler

1975

Eur J Biochem

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The location of amino acid residues within the tobacco mosaic virus protein subunit is discussed. Sequence data, X-ray crystallographic measurements, and the availability of specific residues for enzymic, immunological or chemical reaction are amongst the information used to trace roughly how the tobacco mosaic virus polypeptide chain winds in and out from the virus axis. Published rules for predicting secondary structure are then applied to obtain a diagram of the course of the polypeptide chain. This map should be useful for the interpretation of X-ray diffraction data and already permits an outline of the main features of the inner third of subunit to be suggested.Tobacco mosaic virus (TMV) protein presents a difficult problem for X-ray crystallographic structure determination. It can be crystallised as disks [1,2] but the asymmetric unit is very large (about 600000 daltons) and oriented gels of the virus itself are not sufficiently ordered to yield information to atomic resolution. Therefore, as an aid to the interpretation of current X-ray results, we attempt here to make deductions about the structure of the protein subunit from other available evidence. Such deductions impose limitations on the range of interactions between amino acid residues that may be proposed to explain other experimental data and, of course, the work also represents an exploration of the current state of the art of protein structure prediction.TMV protein is an unusually favourable subject for structure prediction because so much is already known about it. The information summarised here was obtained by many methods, the most important of which is X-ray crystallography, but also including electron microscopy, amino acid sequencing, titration studies and studies of the chemical, enzymic and immunological reactivity of various amino acid residues. The secondary structure of the polypeptide chain is then predicted, using the rules of Chou and Fasman [3,4]. Together these results enable us to propose a diagram of the approximate path of the polypeptide chain. Earlier attempts at partial TMV protein structure prediction have been made by Schiffer and Edmundson [5], and Leberman [7]. We gladly acknowledge that our thinking is based upon the labours of many people, not always explicitly mentioned here. In particular we acknowledge our debt to the crystallographic studies of Dr K. C. Holmes and his colleagues, started in Cambridge and continued, more recently, in Heidelberg. Low-Resolution Structural InformationThe TMV protein subunit contains 158 amino acid residues and has a molecular weight of 17493 [8,9]. Electron microscope and X-ray studies upon the virus (reviewed by Klug and Caspar [lo] and more recently by Barrett et al. [ll]) show that each subunit can be contained within a sector-shaped domain, like a slice of cake, within an angle of about 22". It extends radially from about 20 8, to about 90 8, from the virus helix axis, and is about 25 8, high. The RNA fits between the protein subunits in a groove at a radius of about 40 A,...

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Section: Other Injormationmentioning

confidence: 99%

A Prediction of the Structure of Tobacco-Mosaic-Virus Protein

Durham

Butler

1975

Eur J Biochem

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“…The first crystalline samples of tobacco mosaic virus (TMV) contained 1.3 to 1.77% ash (111); subsequently, attempts were made to determine. whether the metallic ions associated with TMV are merely contaminants, acquired either during the sojourn in the host tissues or during purification, or are actually integral components of the complete virion (73). The evidence obtained points to the latter alternative, inasmuch as the cation composition of TMV neither bears any direct relationship to that of the host fluids nor varies in content during successive ultracentrifugal cycles of purification.…”

Section: Stability Offree Particlesmentioning

confidence: 90%

Roles of metallic ions in host-parasite interactions.

Weinberg¹

1966

Bacteriological Reviews

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“…Based on titration experiments, it was reported that TMV contains groups that titrate with pK a values between 7 and 8 [9], leading to the hypothesis that a carboxylate cluster binds protons with high affinity. In addition, it has also been demonstrated that TMV binds Ca 2+ via these residues [11,12]. In addition, it has also been demonstrated that TMV binds Ca 2+ via these residues [11,12].…”

Section: Introductionmentioning

confidence: 94%

“…These putative residues termed "Caspar-Carboxylates" [9,10] are thought to drive virus disassembly through mutual repulsion upon entering the intracellular environment. In addition, it has also been demonstrated that TMV binds Ca 2+ via these residues [11,12]. The CP folds into a four-helix bundle that is commonly divided into three regions referring to the radial distance from the helical axis [13]: lower radius 20-40 Å , middle radius 40-60 Å , and higher radius 60-90 Å .…”

Section: Introductionmentioning

confidence: 99%

Elucidation of the viral disassembly switch of tobacco mosaic virus

et al. 2019

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Stable capsid structures of viruses protect viral RNA while they also require controlled disassembly for releasing the viral genome in the host cell. A detailed understanding of viral disassembly processes and the involved structural switches is still lacking. This process has been extensively studied using tobacco mosaic virus (TMV), and carboxylate interactions are assumed to play a critical part in this process. Here, we present two cryo‐EM structures of the helical TMV assembly at 2.0 and 1.9 Å resolution in conditions of high Ca2+ concentration at low pH and in water. Based on our atomic models, we identify the conformational details of the disassembly switch mechanism: In high Ca2+/acidic pH environment, the virion is stabilized between neighboring subunits through carboxyl groups E95 and E97 in close proximity to a Ca2+ binding site that is shared between two subunits. Upon increase in pH and lower Ca2+ levels, mutual repulsion of the E95/E97 pair and Ca2+ removal destabilize the network of interactions between adjacent subunits at lower radius and release the switch for viral disassembly.

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Tobacco mosaic virus—A calcium-magnesium coordination complex

Cited by 30 publications

References 16 publications

A Prediction of the Structure of Tobacco-Mosaic-Virus Protein

A Prediction of the Structure of Tobacco-Mosaic-Virus Protein

Roles of metallic ions in host-parasite interactions.

Elucidation of the viral disassembly switch of tobacco mosaic virus

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