[Rutherford]

How do I know whether the AUG codon at the beginning of a genetic code is used for initiation or synthesis of Met, or both?

[Arkcon]

Yes.



 


OK, for many prokaryote proteins, MET is always the first amino acid residue, and is almost always only used for that purpose, subject to post-translational modification.  Eukaryotes use more complex systems.

[Rutherford]

Okay. Still, don't know what to write if I just get a code like: AUG-AAA-... Is it Met-Lys-... or Lys-...?

[Arkcon]

You can't be sure if you have no other information.  But for an exam question just like that, you should call an AUG codon a MET amnio acid residue.

[Rutherford]

I will. Thanks.

[Babcock_Hall]

It depends on whether we are talking about bacterial versus eukaryotic organisms, and the meaning of AUG is context-dependent in both cases.  AUG will always code for an amino acid, either Met or formylMet.  However, in some cases this first amino acid residue is modified or removed later on.

[Babcock_Hall]

Okay. Still, don't know what to write if I just get a code like: AUG-AAA-... Is it Met-Lys-... or Lys-...?

As written, AUG-AAA- means either Met-Lys- or possibly fMet-Lys-, but it could never mean just Lys.

[Rutherford]

It's clear now. Thanks.