Acellular Microbes and Agents

Prions

Pathogenic, misfolded versions of normal cell proteins

Major prion protein PrP

What prion is encoded by the gene PRNP also called CD230 on the p arm of chromosome 20

ZIP metal ion transporters

What class of proteins is it suspected that PrP came from

ZIP metal ion transporters

What class of proteins exhibits a pH dependent ability to bind metal cations with the strongest affinity for copper

3 alpha helices, 2 antiparallel beta sheets, globular domain

What is the secondary structure of a correctly folded PrP protein?

Cell-surface

Where is mature PrP found?

PrP^c, or cellular isoform

What is the correctly folded form of PrP

PrP^Sc

Misfolded, disease-causing form of PrP; associated with scrapie; highly resistant to degradation by proteases

Amyloid Fibrils

Compact, insoluble aggregates in nervous tissue formed by PrP^Sc which resemble beta sheet rich aggregates and the molecular structure of starch

Amyloid Plaques

Extracellular deposits of amyloid fibrils that accumulate within the CNS and disrupt normal structure and function of the NS

Vacuolation

Neurons attempt to compartmentalize prions inside vacuoles, causing enlarged vacuoles that appear like holes when analyzing tissue, causing the spongiform histologic manifestation of prion diseases

Prion Diseases

Rapidly progressive and always fatal

Prion Diseases

May be acquired, familial, or sporadic

Acquired

arising from exposure to prions via medical procedure or via ingestion of prion-containing material including biofluids, animal tissue, or contaminated soil

Familial

Arising from a genetic mutation

Sporadic

Arising from spontaneous mutation

Transmissible spongiform encephalopathies

another name for prion diseases

Stanley B. Prusiner

First person to discover prions in 1982

Prion-like Proteins, prionoids

Misfolded proteins that form amyloid aggregates associated with degenerative diseases that do not complete a full infectious cycle

amyloid-beta

prion-like protein associated with alzheimers disease

tau

prion- like proteins that are associated with neurodegenerative diseases (specific type)

alpha-Synuclein amyloids

associated with parkinsons disease; accumulate inside neurons (substantia nigra, locus coeruleus) and form lewy bodies

Viroid

Small, single-stranded circular RNA molecules without a protein coat that infect flowering plants; the RNA often possesses a highly compact, intricate secondary structure

Rolling Circle Amplification

How viroids replicate using the host’s RNA polymerase II

Viroids

Accumulates and disrupts normal cellular processes and gene regulation

Viroids

What are these examples of: potato spindle tuber ____, coconut cadang-cadang ____; tomato apical stunt ___

Viruses

Obligate intracellular pathogens that posses DNA or RNA

Viruses

10s to 100s of nanometers in length

Virions

viral particles that consist of the genetic material encapsulated by the capsid

Prophage

Viral DNA incorporated into cellular DNA during lysogenic cycle

Capsid

protein coating on a virus

Viral envelope

lipid layer coating some viruses

Capsomeres

subunits that make up a capsid

Protomers

protein subunits that make up capsomeres

Bacteriophages

Viruses that infect bacteria; usually have genes composed of DNA

Helical

Capsid shape that appears to be rod-shaped or filamentous; includes tobacco mosaic virus and ebola

Polyhedral

Capsid shape that takes the shape of a regular, convex icosahedron (20-sided 3D shape composed of equilateral triangles); includes adenoviruses, picornaviruses, including Hep A and polio

Spherical

Type of virus; appear spherical under microscope due to viral envelope; HIV-1 and 2, herpes, influenza

Baltimore Classification

Divides viruses into seven different groups on the basis of their genetic material; created in 1971 by the virologist David Baltimore, this system is often used alongside and has now been partially incorporated into standard viral taxonomy.

Class I

Class of virus that has double-stranded DNA

Class II

Class of virus that have single-stranded DNA

Class III

Class of virus that have double-stranded RNA

Class IV

Class of virus that have positive-sense single-stranded RNA

Class V

Class of virus that have negative-sense single-stranded RNA

Class VI

Class of virus that are RNA retroviruses

Class VII

Class of virus that are DNA retroviruses

Lytic

Type of infection where the virus injects its genome into the host cell; cell begins making mRNA from viral DNA, which is made into viral proteins; cell shuts down and virus uses cell to replicate; enough viruses are made and cell bursts/lyses; 100s or 1000s are released

Lysogenic

Type of infection where a virus integrates its DNA into the host cell’s DNA; the prophage remains dormant in the cell’s DNA for several generations before becoming active, leaving the cell’s DNA, and directing synthesis of new viral proteins; allows virus to enter more cells; HIV

Satellites

Subviral particles that cannot complete the cycle of infection independently; dependent on both host machinery and presence of helper virus for proper replication; much shorter than viral genomes

Satellite Virus

Genome encodes a capsid

Satellite Nucleic Acids

Genome relies on helper viruses for encapsidation

Virophages

A type of subviral particle similar to satellite viruses; require help of co-infecting virus; remain in cytoplasm of infected host cells and hijack the cytoplasmic virus factories established by their co-infecting viruses, a parasitic; reduce the replication efficiency (and, therefore, also the infectivity) of co-infecting viruses, which may aid in host cell survival

Virophages

Always have circular or linear double-stranded DNA genomes; usually 16-18 kb in length; display parasitic relationship with co-infecting giant virus

giant virus

Have larger genomes and large capsids and belong to phylum Nucleocytoviricota

Nucleocytoplasmic large DNA viruses

can perform viral replication in either the nucleus or cytoplasm of host cells; encode enzymes involved in DNA repair, replication, and transcription, which allows them to establish cytoplasmic virus factories that facilitate genome replication in addition to protein synthesis and virion assembly

Virusoid

A type of satellite; viroid that has been enclosed in a protein capsid of another virus; depends on both the helper virus and the host cell RNA polymerase II for replication; have circular, single-stranded RNA genomes