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"Rattlesnake" structure of a filamentous plant RNA virus built of two capsid proteins.

ABSTRACT: Elongated particles of simple RNA viruses of plants are composed of an RNA molecule coated with numerous identical capsid protein subunits to form a regular helical structure, of which tobacco mosaic virus is the archetype. Filamentous particles of the closterovirus beet yellow virus (BYV) reportedly contain approximately 4000 identical 22-kDa (p22) capsid protein subunits. The BYV genome encodes a 24-kDa protein (p24) that is structurally related to the p22. We searched for the p24 in BYV particles by using immunoelectron microscopy with specific antibodies against the recombinant p24 protein and its N-terminal peptide. A 75-nm segment at one end of the 1370-nm filamentous viral particle was found to be consistently labeled with both types of antibodies, thus indicating that p24 is indeed the second capsid protein and that the closterovirus particle, unlike those of other plant viruses with helical symmetry, has a "rattlesnake" rather than uniform structure.

SUBMITTER: Agranovsky AA

PROVIDER: S-EPMC42239 | biostudies-other | 1995 Mar

REPOSITORIES: biostudies-other

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"Rattlesnake" structure of a filamentous plant RNA virus built of two capsid proteins.

Agranovsky A A AA Lesemann D E DE Maiss E E Hull R R Atabekov J G JG

Proceedings of the National Academy of Sciences of the United States of America 19950301 7

Elongated particles of simple RNA viruses of plants are composed of an RNA molecule coated with numerous identical capsid protein subunits to form a regular helical structure, of which tobacco mosaic virus is the archetype. Filamentous particles of the closterovirus beet yellow virus (BYV) reportedly contain approximately 4000 identical 22-kDa (p22) capsid protein subunits. The BYV genome encodes a 24-kDa protein (p24) that is structurally related to the p22. We searched for the p24 in BYV parti ...[more]

PMID: 7708667

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Project description:Leishmania parasites cause a variety of symptoms, including mucocutaneous leishmaniasis, which results in the destruction of the mucous membranes of the nose, mouth, and throat. The species of Leishmania carrying Leishmania RNA virus 1 (LRV1), from the family Totiviridae, are more likely to cause severe disease and are less sensitive to treatment than those that do not contain the virus. Although the importance of LRV1 for the severity of leishmaniasis was discovered a long time ago, the structure of the virus remained unknown. Here, we present a cryo-electron microscopy reconstruction of the virus-like particle of LRV1 determined to a resolution of 3.65 Å. The capsid has icosahedral symmetry and is formed by 120 copies of a capsid protein assembled in asymmetric dimers. RNA genomes of viruses from the family Totiviridae are synthetized, but not capped at the 5' end, by virus RNA polymerases. To protect viral RNAs from degradation, capsid proteins of the L-A totivirus cleave the 5' caps of host mRNAs, creating decoys to overload the cellular RNA quality control system. Capsid proteins of LRV1 form positively charged clefts, which may be the cleavage sites for the 5' cap of Leishmania mRNAs. The putative RNA binding site of LRV1 is distinct from that of the related L-A virus. The structure of the LRV1 capsid enables the rational design of compounds targeting the putative decapping site. Such inhibitors may be developed into a treatment for mucocutaneous leishmaniasis caused by LRV1-positive species of Leishmania IMPORTANCE Twelve million people worldwide suffer from leishmaniasis, resulting in more than 30 thousand deaths annually. The disease has several variants that differ in their symptoms. The mucocutaneous form, which leads to disintegration of the nasal septum, lips, and palate, is caused predominantly by Leishmania parasites carrying Leishmania RNA virus 1 (LRV1). Here, we present the structure of the LRV1 capsid determined using cryo-electron microscopy. Capsid proteins of a related totivirus, L-A virus, protect viral RNAs from degradation by cleaving the 5' caps of host mRNAs. Capsid proteins of LRV1 may have the same function. We show that the LRV1 capsid contains positively charged clefts that may be sites for the cleavage of mRNAs of Leishmania cells. The structure of the LRV1 capsid enables the rational design of compounds targeting the putative mRNA cleavage site. Such inhibitors may be used as treatments for mucocutaneous leishmaniasis.

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"Rattlesnake" structure of a filamentous plant RNA virus built of two capsid proteins.

Publications

"Rattlesnake" structure of a filamentous plant RNA virus built of two capsid proteins.

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