Exam 22: Protein Synthesis, posttranslational Modification, and Transport

A protein is targeted to the plasma membrane.Its final functional location is as a subunit of a transmembrane protein that interacts with the central subdomain of the membrane.Analysis of this protein would most likely show modification with a

Contrast the discrimination at the active site and at the editing site of aminoacyl-tRNA synthetases,so that combined they ensure that tRNAs are charged with the correct amino acid.

What characteristics of eukaryotic mRNA are recognized through specific interactions during the formation of the translation initiation complex?

Why does the genetic code require triplet codons to code for the 20 different amino acids? Why would duplet codons be inadequate to perform the job?

Nirenberg and Matthaei determined the genetic code experimentally by using a cell-free translation system.Two components,however,were restricted in their system.One was the use of a single type of mRNA.What was the other component that was restricted? How did this restriction allow them to determine the genetic code?

Which of the following mRNA codons would NOT be recognized by a tRNA that is charged with an amino acid?

After the initiation complex is complete,what occurs next in the process of translation?

Secondary downstream of the cap structure in the mRNA is unwound during the __________ step of translation.

A nucleophilic amino group of the amino acid bound to the terminus of A-site tRNA attacks the electrophilic carbonyl carbon in the ester bond between the terminus of P-site tRNA and its bound amino acid during the __________ step of translation.

Aminoacyl-tRNA synthetase contains two binding sites.Describe the consequence of a mutation that changed the specificity of the amino acid binding site of an aminoacyl-tRNA synthetase from Glu to Asp.

The eukaryotic 48S preinitiation complex is purified and the components are identified.Which of the following would be found in this complex?

All glycoproteins have __________ covalently added posttranslationally.

The of the two combined catalytic steps of tRNA synthetase is near equilibrium.How does this reaction occur in an essentially irreversible fashion in a cell?

Although the genetic code is considered universal,this may not be fully true when comparing the human nuclear code with the human mitochondrial code.Describe how and provide a specific example.

The wobble hypothesis was first proposed by

A full catalytic cycle of an aminoacyl-tRNA synthetase generates __________ as a product.

Ribosomal rRNA interacts with all EXCEPT __________ during the process of translation.

During the import of one protein from the cytosol to the nucleus via Ran-dependent nuclear import,__________ high-energy phosphate molecule(s)are hydrolyzed.

Below are examples of sequences from seven different E.coli genes.The underlined sequences are known as __________ sequences and the bolded AUG sequences are known as the __________ codon.

Differentiate among the trafficking of vesicles coated with COPI,COPII,or clathrin.