Concept explainers
Not all proteins are made from the RNA genome of bacteriophage MS2 in the same amounts. Can you explain why? One of the proteins functions very much like a repressor, but it functions at the translational level. Which protein is it and how does it function?
The RNA bacteriophage are very small, around 25 nm in diameter with icosahedral virion structure. For example, MS2 (having positive strand RNA) virus has a small genome, which encodes only four types of proteins. These are 1) Mutation proteins, which are present as a single copy in a mature virion, 2) coat protein, 3) lysis protein and 4) subunit of RNA replicase (it is the enzyme, which replicates the viral RNA). RNA replicase protein consists of one virus encoded polypeptide and many peptides of the host.
Explanation of Solution
The RNA of phage MS2 is folded in a complicated way, thereby, leading to formation of an extensive secondary structure. The translation at coat protein site on m-RNA starts very early upon viral infection, as it is most accessible to translation machinery among the four AUG translation sites. The m-RNA replicase enzyme also translate early. Since coat proteins translate early, they start increasing in number in number within the cell. Coat proteins start binding to RNA at AUG region, which is the initiation site for replicase protein and shit down the production of replicase. Therefore, coat protein also acts like a repressor protein. Also due to extensive folding of RNA limited copies maturation protein is produced even though it is present at 5’ end. Thus translation regulation occurs due to the folding of RNA, thereby, producing limited proteins for viral assemble. Coat protein, however is required in large quantity, therefore it is majorly produced.
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Chapter 10 Solutions
EBK BROCK BIOLOGY OF MICROORGANISMS
- You’re going for a bike ride, and as your muscles work harder, your body needs to produce more of the enzyme. You now know genes are transcribed from DNA into RNA in the nucleus and translated from RNA into proteins by ribosomes. Explain the steps of its creation from DNA to protein. Aside for having a nasty inhibitor around like the one from that insecticide, how else might an enzyme end up being non-functioning? During transcription, a base substitution occurred. Explain two reasons why this change in nucleotide sequence could result in no change to the protein.arrow_forwardThe E. coli genome contains approximately 4639 kb. (a) How many copies of the 6-bp recognition sequence for the trp repressor would be expected to occur in the E. coli chromosome? (b) Explain why it is advantageous for the trp repressor to be a dimer that recognizes two adjacent 6-bp sequences.arrow_forwardThe genetic code is thought to have evolved to maximize genetic stability by minimizing the effect on protein function of most substitution mutations (single-base changes). We will use the six arginine codons to test this idea. Consider all of the substitutions that could affect all of the six arginine codons.(a) How many total mutations are possible?(b) How many of these mutations are “silent,” in the sense that the mutantcodon is changed to another Arg codon?(c) How many of these mutations are conservative, in the sense that an Argcodon is changed to a functionally similar Lys codon?arrow_forward
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- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning