Question

Biochemistry project 2

To have manageable peptides for sequencing by Edman Degradation, you first reduced all of the disulfide bonds and then digested the protein with cyanogen bromide. You then isolated one of the peptide fragments from this digest by isoelectric focusing, split it into two aliquots, and subjected one aliquot to tryptic digest and one aliquot to chymotryptic digest. After isolating all of the peptides from these digests, you sequence the peptides. The following are the sequences you obtained

Tryptic peptides –

LFESFGDLFTPDAVM

VNVDEVGGEALGR

LLVVYPWTQR

SAVTALWGK

MVHLTPEEK

Chymotryptic peptides -

GKVNVDEVGGEALGRLLVVY

MVHLTPEEKSAVTALW

TPDAVM

TQRLF

GDLF

ESF

PW

What is the sequence for the full peptide and, using the NCBI web site, determine what protein family it comes from?

Answer 1

Answer:

1):

• ​​​​ an mRNAlecule binds to the small ribosomal subunit at the mRNA biding site.
• AspecialtRNA, called initiator tRNA, binds to the start codon (AUG) on mRNA, where translation begins.
• The tRNA anticodon (UAC) attaches to the mRNA codon (AUG) by pairing between the complementary bases.
• Besides being the start codon, AUG is also the codon for the amino acid methionine.
• Thus, methionine is always the first amino acid in a growing polypeptide

2):

• Next, the large ribosomal subunit attaches to the small ribosomal subunit-mRNA complex, creating a functional ribosome.
• The initiator tRNA, with its amino acid (methionine), fits into the P site of the ribosome.

3):

• The anticodon of another tRNA with its attached amino acid pairs with the second mRNA codon at the A site of the ribosome.

4):

• A component of the large ribosomal subunit catalyzes the formation of a peptide bond between methionine, which separates from its tRNA at the P site, and the amino acid carried by the tRNA at the A site.

5):

• ​​​​​ After peptide bond formation, the empty tRNA at the P site detaches from the ribosome, and the ribosome shifts the mRNA strand by one codon.
• The tRNA in the A site bearing the two-peptide protein shifts into the P site, allowing another tRNA with its amino acid to bind to a newly exposed codon at the A site.
• Steps 3 through 5 occur repeatedly, and the protein lengthens progressively.

6):

• Protein synthesis ends when the ribosome reaches a stop codon at the A site, which causes the completed protein to detach from the final tRNA.
• When the tRNA vacates the A site, the ribosome splits into its large and small subunits.In your book (probably), the titles it gives are

1: Messenger RNA Production
2: Messenger RNA Attaches to a Ribosome
3: Transfer RNA Attaches to Messenger RNA
4: Protein Production

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