Question

There are many forms of processing and polishing that can take place for a newly synthesized polypeptide.

Identify each example of polypeptide processing and polishing in Bacteria.

Select all that apply.   

Group of answer choices

Cleavage of a nucleic acid residue

Addition of a formyl group to Methionine

Incorporation of a metal atom

Peptide bond rotation

Re-folding with the aid of a chaperone

Addition of a signal peptide

Answer 1

The forms of processing and polishing that can take place for a newly synthesized polypeptide in bacteria are:
Addition of a formyl group to Methionine: This modification is done after methionine has been loaded onto tRNAfMet by aminoacyl-tRNA synthetase. Methionine itself can be loaded either onto tRNAfMet or tRNAMet during translation.

Incorporation of a metal atom: in order to form metalloproteins, metallic ions are inserted in the protein. Examples: Metalloenzymes are enzyme proteins containing metal ions (metal cofactors), which are directly bound to the protein or to enzyme-bound nonprotein components (prosthetic groups).

Peptide bond rotation: Peptide bonds have a planar, trans, configuration and undergo very little rotation or twisting around the amide bond that links the α-amino nitrogen of one amino acid to the carbonyl carbon of the next. This effect is due to amido–imido tautomerization.

Re-folding with the aid of a chaperone: Chaperones are a group of proteins that have functional similarity and assist in protein folding. They are proteins that have the ability to prevent non-specific aggregation by binding to non-native proteins.

Addition of a signal peptide: Signal peptides may help to enforce proper topology of the polypeptide during translocation by what is known as the positive-inside rule.