Answer:
The N-terminal aminoacid is Metionin.
Explanation:
Before answering the question, let us remember the meaning of the term <em>amino terminus</em>. <em>Terminus </em>refers to the extremes of the polypeptide. During translation, rRNA and tRNA read mRNA in 5´ to 3´ direction. The first extreme to be translated carries the <em>amino-terminal</em> group, while the other extreme carries the <em>carboxy-terminus </em>group<em>. </em>
Conventionally, proteins are written from left to right, beginning by the N-terminal extreme carrying the free amine group, and ending by the C-terminal extreme carrying the carboxyl free group. However, we need to know that the free amine group actually places at the end of a protein.
<u>Transcription:</u>
Transcription occurs in the nucleus where the template DNI strand is read in direction 3´→ 5´ to build the mRNA molecule in direction 5´→ 3´.
template DNI strand ⇒ 5'-TAGAACGCCTCGAAATTTCATACT-3'
mRNA ⇒ 3´-AUCUUGCGGUGCUUUAAAGUAUGA- 5´
<u>Translation</u>:
Translation occurs in the cytoplasm. rRNA and tRNA read mRNA in the direction 5´→ 3´ to build the protein.
Protein synthesis initiates in the AUG start codon -Metionin-, and ends when reaching either of the stop codons UAA, UAG, UGA.
The first portion of mRNA is not read nor translated. This is the <em>untranslated region (UTR)</em>, placed before the strat codon.
mRNA ⇒ 3´-AUCUUGCGGUGCUUUAAAGUAUGA- 5´
Remember that transcription occurs from 5´ to 3´ extremes, so we need to read the codons in this direction too, beginning on the 5´ extreme.
First, we need to find the initiation codon: AUG coding for Metionin.
mRNA ⇒ 3´-AUCUUGCGGUGCUUUAAA<u>GUA</u>UGA- 5´
Met
mRNA ⇒ 3´-AUCUUGCGGUGCUUU<u>AAA</u>GUAUGA- 5´
Lys Met
mRNA ⇒ 3´-AUCUUGCGGUGC<u>UUU</u>AAAGUAUGA- 5´
Phe Lys Met
mRNA ⇒ 3´-AUCUUGCGG<u>UGC</u>UUUAAAGUAUGA- 5´
Arg Phe Lys Met
mRNA ⇒ 3´-AUCUUG<u>CGG</u>UGCUUUAAAGUAUGA- 5´
Gly Arg Phe Lys Met
mRNA ⇒ 3´-AUC<u>UUG</u>CGGUGCUUUAAAGUAUGA- 5´
Val Gly Arg Phe Lys Met
mRNA ⇒ 3´-<u>AUC</u>UUGCGGUGCUUUAAAGUAUGA- 5´
Leu Val Gly Arg Phe Lys Met
The N-terminal aminoacid is then Metionin.