Question

Augu Q46. Below is a DNA sequence from a yeast GPCR gene. Using RNA sequencing methods you have obtained the following partial 5' sequence for the MRNA transcribed from this gene: 5'-GGUCCAU... 5'GTATAAGAAGCACTCTACCTCAATGGGTCCATGGGAGAAGGTAGGCATGTGTATTTGACAAAGGGA i. What are the most likely six N-terminal amino acids for the above gene? (2 pts) Examine the other reading frames. Explain why you can exclude those other possible reading frames from consideration (one or two reasons depending upon the frame). (2 pts) Circle the portion of the gene above that is likely to be the promoter region and contain a transcription factor binding site. (2 pts) Just after the coding region you identified above is a stretch of sequence that is predicted to encode several hydrophobic amino acids in a row. Mutations in this region results in cytosolically distributed but correctly folded yet aggregated receptors. Explain the likely role of this sequence near the N- terminus of this GPCR protein. (2 pts) iv.

Answer 1

Answer :)

The mRNA sequence is as the following:

5’ GUAUAAGAAGCACUCUACCUCAAUGGGUCCAUGGGAGAAGGUAGGCAUGUGUAUUUGACAAAGGGA 3’

Answer i:)

The amino acid chain of the above mRNA strand (based on the open reading frame mentioned in the second part of the answer):

MET GLY GLU GLY ARG HIS VAL TYR LEU THR LYS GLY

Therefore, the six terminal amino acids are VAL TYR LEU THR LYS GLY

Answer ii:)

The reading frame of the above mRNA is as bellow:

AUGGGAGAAGGUAGGCAUGUGUAUUUGACAAAGGGA

Protein sequence: MET GLY GLU GLY ARG HIS VAL TYR LEU THR LYS GLY

The protein sequence does not contain stop codon; therefore, it is a reading frame. The minimum size of an open reading frame is 100 codons. Therefore, in this reading frame, we suppose that there must be 100 codons until a stop codon does not come.

The other reading frame:

1. 5’ AUGGGUCCAUGGGAGAAGGUAGGCAUGUGUAUUUGA 3’

Protein sequence: MET GLY PRO TRP GLU LYS VAL GLY MET CYS ILE STOP

We chose the reading frame from the start codon (AUG). This reading frame is started with AUG codon but contains stop codon and does not reach to minimum 100-codon length.

2. AUGUGUAUUU

Protein sequence: MET CYS ILE STOP

This reading frame is too short to consider as an open reading frame.

Answer iii:)

The red circle is showing the possible promoter region i.e. TATA box.

Q46. Below is a DNA sequence from a yeast GPCR gene. Using RNA sequencing methods you have obtained the following partial 5' sequence for the MRNA transcribed from this gene: 5'-GGUCCAU... 5'GTATAAGAAGCACTCTACCTCAATGGGTCCATGGGAGAAGGTAGG CATGTGTATTTGACAAAGGGA i. What are the most likely six N-terminal amino acids for the above gene? (2 pts) Examine the other reading frames. Explain why you can exclude those other possible reading frames from consideration (one or two reasons depending upon the frame). (2 pts) i. Circle the portion of the gene above that is likely to be the promoter region and contain a transcription factor binding site. (2 pts) Just after the coding region you identified above is a stretch of sequence that is predicted to encode several hydrophobic amino acids in a row. Mutations in this region results in cytosolically distributed but correctly folded yet aggregated receptors. Explain the likely role of this sequence near the N- terminus of this GPCR protein. (2 pts) iv.

Answer iv:)

The possible amino acid sequence is MET GLY GLU GLY ARG HIS VAL TYR LEU THR LYS GLY in which the terminal amino acid Glycine supports in the flexibility of the protein.

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