Textbook Chapter 2 Virus Structure and Assembly Flashcards
how do viruses enclose their nucleic acid genomes?
in protein capsids, some v also have an internal or external lipid containing envelope
why are capsids of small viruses highly symmetrical?
because they are constructed from one or a small number of identical subunits
what is the symmetry for capsids that are closed, quasi spherical shells?
icosahedral symmetry with fivefold, threefold, and twofold symmetry axes
how many identical subunits are needed to construct the smallest capsids with icosahedral symmetry?
60
larger capsids with icosahedral symmetry usually are made from what subunits?
60 x T subunits where T is the triangulation number, larger capsids may also have additional capsid proteins that strengthen the structure
many capsid proteins have a common three dimensional fold called what?
jelly roll beta barrel, which provides a rigid, brick like structure
tubular capsids have helical symmetry, and their length depends on what?
the length of the enclosed nucleic acid genome
many but not all viral envelopes are derived from what?
by budding from preformed cellular membranes
viral envelopes usually incorporate what ?
viral glycoproteins with a transmembrane anchor
some capsids are assembled around the what?
nucleic acid and genome
how are other capsids assembled?
pre assembled and the genome is stuffed into the capsid
do scaffolding proteins that help assemble the the capsid stay with the capsid?
no, they are ejected and do not form part of the mature capsid
what do many viral genomes contain that recognizes specific packaging sequences?
capsid proteins, ensuring that only intact genomes are encapsidated
