![Genome
The TMV genome consists of a 6.3–6.5 kb single-
stranded (ss) RNA.
The 3’-terminus has a tRNA-like structure, and the 5’
terminus has a methylated nucleotide cap.
(m7G5’pppG).
The genome encodes 4 open reading frames (ORFs),
two of which produce a single protein due
to ribosomal readthrough of a leaky UAG stop codon.
The 4 genes encode a replicase (with methyltransferase
[MT] and RNA helicase [Hel] domains), an RNA-
dependent RNA polymerase, a so-called movement
protein (MP) and a capsid protein (CP).[18]](https://image.slidesharecdn.com/structureoftmv-201001040030/85/Structure-of-TMV-and-Bacteriophage-5-320.jpg)
Structure of TMV and Bacteriophage
- 1. Microbial Taxonomy and Diversity – Structure of Virus Dr. S. Sivasankara Narayani Assistant Professor Department of Microbiology Ayya Nadar Janaki Ammal College Sivakasi 01-10-2020 Dr.SS
- 2. UNIT–III CLASSIFICATION OFVIRUS Viruses: Physical, chemical and biological properties. Baltimore classification. Types of viruses based on structure and Host. Cultivation of viruses: Cell line - embryonated eggs - cytopathic effect. Structure of viruses: TMV- T4bacteriophage. Replication of virus: Lytic and lysogenic cycle. Phage typing. 01-10-2020 Dr.SS
- 3. TMV Tobacco mosaic virus has a rod-like appearance. Its capsid is made from 2130 molecules of coat protein one molecule of genomic single strand RNA, 6400 bases long. The coat protein self-assembles into the rod-like helical structure (16.3 proteins per helix turn) around the RNA, which forms a hairpin loop structure. The protein monomer consists of 158 amino acids which are assembled into four main alpha-helices, which are joined by a prominent loop proximal to the axis of the virion. Virions are ~300 nm in length and ~18 nm in diameter. Negatively stained electron microphotographs show a distinct inner channel of radius ~2 nm. The RNA is located at a radius of ~4 nm and is protected from the action of cellular enzymes by the coat protein. X-ray fiber diffraction structure of the intact virus was studied based on an electron density map at 3.6 Å resolution. Inside the capsid helix, near the core, is the coiled RNA molecule, which is made up of 6,395 ±10 nucleotides
- 4. Structure
- 5. Genome The TMV genome consists of a 6.3–6.5 kb single- stranded (ss) RNA. The 3’-terminus has a tRNA-like structure, and the 5’ terminus has a methylated nucleotide cap. (m7G5’pppG). The genome encodes 4 open reading frames (ORFs), two of which produce a single protein due to ribosomal readthrough of a leaky UAG stop codon. The 4 genes encode a replicase (with methyltransferase [MT] and RNA helicase [Hel] domains), an RNA- dependent RNA polymerase, a so-called movement protein (MP) and a capsid protein (CP).[18]
- 6. T4 Bacteriophage Viruses infecting bacteria are called Bacteriophages . It literally means ‘eaters of bacteria’ (Gr: Phagein = to eat). Phages are abundant in soil, sewage water, fruits, vegetables , milk The T4 phage is tadpole shaped and consists of head, collar, tail, base plate and fibres. The head is hexagonal which consists of about 2000 identical protein subunits. The long helical tail consists of an inner tubular core which is connected to the head by a collar. There is a base plate attached to the end of tail. The base plate contains six spikes and tail fibres. These fibres are used to attach the phage on the cell wall of bacterial host during replication. A dsDNA molecule of about 50 µm is tightly packed inside the head. The DNA is about 1000 times longer than the phage itself
- 7. Structure
- 8. Genome Phage T4 has provided countless contributions to the paradigms of genetics and biochemistry. Its complete genome sequence of 168,903 bp encodes about 300 gene products.
- 10. Questionsto think Structure of TMV Structure of T4 01-10-2020 Dr.SS
- 11. 01-10-2020 Dr.SS