Caspar Carboxylates: The Structural Basis of Tobamovirus Disassembly

Wang, Hong; Planchart, Antonio; Stubbs, Gerald

doi:10.1016/s0006-3495(98)77822-1

Cited by 46 publications

(37 citation statements)

References 21 publications

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“…Low-calcium concentration and high pH were long thought to be the trigger for TMV virion uncoating (6,13). Higher calcium Fig.…”

Section: Discussionmentioning

confidence: 99%

“…CP has several clusters of acidic amino acids (including a cluster of negative charges formed by an aspartic acid residue and a phosphate moiety of the viral RNA) that are stable outside of cells, where calcium-ion and proton levels are relatively high, but repel one another in the low-calcium, low-proton conditions inside cells. CP mediates assembly and disassembly through these carboxyl-carboxylate or phosphatecarboxylate pairs that switch states at different calcium and proton concentrations (11,13,14). Such a regulation is common in plant viruses.…”

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confidence: 99%

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Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches

Zhou

2011

Proc. Natl. Acad. Sci. U.S.A.

111

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Helical assemblies such as filamentous viruses, flagella, and F-actin represent an important category of structures in biology. As the first discovered virus, tobacco mosaic virus (TMV) was at the center of virus research. Previously, the structure of TMV was solved at atomic detail by X-ray fiber diffraction but only for its dormant or high-calcium-concentration state, not its low-calcium-concentration state, which is relevant to viral assembly and disassembly inside host cells. Here we report a helical reconstruction of TMV in its calcium-free, metastable assembling state at 3.3 Å resolution by cryo electron microscopy, revealing both protein side chains and RNA bases. An atomic model was built de novo showing marked differences from the high-calcium, dormant-state structure. Although it could be argued that there might be inaccuracies in the latter structure derived from X-ray fiber diffraction, these differences can be interpreted as conformational changes effected by calcium-driven switches, a common regulatory mechanism in plant viruses. Our comparisons of the structures of the low-and highcalcium states indicate that hydrogen bonds formed by Asp116 and Arg92 in the place of the calcium ion of the dormant (highcalcium) state might trigger allosteric changes in the RNA basebinding pockets of the coat protein. In turn, the coat protein-RNA interactions in our structure favor an adenine-X-guanine (A*G) motif over the G*A motif of the dormant state, thus offering an explanation underlying viral assembly initiation by an AAG motif.H elical assemblies represent a very important class of biological structures, performing various tasks for the proper functions of life or executing malicious functions in disease. For example, protein helical assemblies such as cytoskeletal networks and muscle fibers are essential components in our bodies (1, 2). Other helical assemblies include bacterial flagella and secretion systems. Helical viruses, such as tobacco mosaic virus (TMV), account for a major fraction of the virus kingdom. Such helical structures, bearing a special kind of 2D periodicity and potential flexibility, are difficult for structural determination to atomic resolution by conventional methods including X-ray crystallography and NMR. Thus, the molecular mechanisms of action in many of these systems are not understood to atomic detail. Even for TMV, the first virus ever isolated and extensively studied (3) by both X-ray diffraction (e.g., 4-8) and cryo electron microscopy (cryoEM) (9, 10), we still do not know its structure at atomic detail in a state that is relevant to its assembly and disassembly processes, and the underlying mechanisms of these processes remain unknown.The viral RNA of TMV is infectious by itself, but RNA on its own is very unstable. The addition of a 17-kDa coat protein (CP) around the RNA protects the RNA from degrading and makes TMV very stable. The assembly of a rod-shaped virion begins at a two-turn helical CP complex, called the 20S aggregate (11), which recognizes the initiation moti...

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“…Low-calcium concentration and high pH were long thought to be the trigger for TMV virion uncoating (6,13). Higher calcium Fig.…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches

Zhou

2011

Proc. Natl. Acad. Sci. U.S.A.

111

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“…A comparative model of the CPCg was built using MODELLER v.8 (Sali & Blundell, 1993). Template coordinates were taken from the closely related ribgrass mosaic virus CP, PDBid: 1RMV (Wang et al, 1997(Wang et al, , 1998 possessing 95.5 % sequence identity and 89.8 % of positive residues with CPCg. Subsequently, the four CP mutant variants: P21L, R46G, S54K and P21L-S54K were modelled using the build mutant module implemented in MODELLER.…”

Section: Methodsmentioning

confidence: 99%

Structure–function relationship between the tobamovirus TMV-Cg coat protein and the HR-like response

Ehrenfeld

González

Cañón

et al. 2008

Journal of General Virology

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The tobamovirus TMV-Cg induces an HR-like response in Nicotiana tabacum cv. Xanthi nn sensitive plants lacking the N or N9 resistance genes. This response has been characterized by the appearance of necrotic lesions in the inoculated leaf and viral systemic spread, although the defence pathways are activated in the plant. A previous study demonstrated that the coat protein (CP) of TMV-Cg (CPCg) was the elicitor of this HR-like response. We examined the influence of four specific amino acid substitutions on the structure of CPCg, as well as on the development of the host response. To gain insights into the structural implications of these substitutions, a set of molecular dynamic experiments was performed using comparative models of wild-type and mutant CPCg as well as the CP of the U1 strain of TMV (CPU1), which is not recognized by the plants. A P21L mutation produces severe changes in the three-dimensional structure of CPCg and is more unstable when this subunit is laterally associated in silico. This result may explain the observed incapacity of this mutant to assemble virions. Two other CPCg mutations (R46G and S54K) overcome recognition by the plant and do not induce an HR-like response. A double CPCg mutant P21L-S54K recovered its capacity to form virions and to induce an HR-like response. Our results suggest that the structural integrity of the CP proteins is important for triggering the HR-like response.

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“…12,27 In TMV, there are two carboxyl-carboxylate pairs: high radius, involving axial Glu50-Asp77 (subunit 16), and low radius, involving lateral intersubunit interactions Glu95/ Glu97/Asp109-Glu106 (subunit 1). The influence of carboxylates on viral disassembly has been well studied with TMV.…”

Section: Protein-protein Interactionmentioning

confidence: 99%

“…If Arg122 is changed to His122, how do HLSV and SHMV CP recognize guanine 1? While carboxyl-carboxylate interactions in Tobamoviruses are the main driving force for virus disassembly, 12 they are not conserved during Tobamovirus evolution. 3,5,7 Does this mean that these interactions in HLSV would be different from those in other Tobamoviruses?…”

Section: Introductionmentioning

confidence: 99%

Structure of Hibiscus Latent Singapore Virus by Fiber Diffraction: A Nonconserved His122 Contributes to Coat Protein Stability

Tewary

Oda

Kendall

et al. 2011

Journal of Molecular Biology

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Caspar Carboxylates: The Structural Basis of Tobamovirus Disassembly

Cited by 46 publications

References 21 publications

Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches

Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches

Structure–function relationship between the tobamovirus TMV-Cg coat protein and the HR-like response

Structure of Hibiscus Latent Singapore Virus by Fiber Diffraction: A Nonconserved His122 Contributes to Coat Protein Stability

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