Help me answer this question please?: A few amino acids are post-translationally

Question

Help me answer this question please?:

A few amino acids are post-translationally removed from the C-terminal end of the beta-lactamase enzyme from B. imaginarium (i.e. - after it is translated and released from the ribosome, a protease chews off a few amino acids). The wild-type enzyme, which has had the amino acids removed from the C’-terminus, is 327 amino acids in length and the C-terminal amino acids are shown below aligned with the C-terminal amino acids of a frameshift mutant, which is not processed at its C-terminus. The wildtype and frameshift mutant have identical coding sequences except for the insertion or deletion of a single nucleotide in the sequences encoding the C-terminal region of the protein.

Use this information to answer the questions below.

AA#: 327

wild-type: Asn Met Asn Gly Lys

mutant: Asn Met Ile Trp Gln Met Cys Asp Met Lys Asp

A. What was the mutational event that gave rise to the frameshift mutant? (identify which codon contains the inserted or deleted nucleotide and the position within the codon where the mutation occurred.

B. Deduce the number of amino acids in the wild-type enzyme prior to processing of the C-terminus and, as far as possible, the actual sequence of the C-terminus of the wild-type enzyme

Explanation / Answer

Answer:

A. wild-type: Asn Met Asn Gly Lys

       mutant: Asn Met Ile Trp Gln Met Cys Asp Met Lys Asp

The insertion took place in the codon encoding for Asn (underlined above, amino acid 325) in the wild type.

AAT encodes for Asn. A 'T' got inserted in between the two A of 'AAT' giving rise to ATAT. (ATA encodes for Ile).

Thus, this gave rise to the frame shift mutation.

B. Wild type sequence (after cleavage):

wild-type:                               Asn Met Asn Gly Lys

Nucleotide sequence:         aac atg aat ggc aaa

Mutant:                                  Asn Met Ile    Trp   Gln    Met Cys Asp   Met   Lys   Asp

Nucleotide sequence:              aac atg   ata    tgg   caa    atg   tgc   gat    atg    aaa    gat

So, the sequence of the uncleaved wild type protein can be obtained if we remove the insertion 'T' previously described in answer (A).

Nucleotide sequence of wild type uncleaved protein: aac atg   aa    tgg   caa    atg   tgc   gat    atg    aaa    gat

Protein sequence: Asn Met Asn Gly Lys Cys Ala Ile Stop

Therefore, number of amino acids in the wild-type enzyme prior to processing of the C-terminus: 330 amino acids (excluding Stop)

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.