Zitat des Tages über Amino:
It is one of the more striking generalizations of biochemistry - which surprisingly is hardly ever mentioned in the biochemical textbooks - that the twenty amino acids and the four bases, are, with minor reservations, the same throughout Nature.
A final proof of our ideas can only be obtained by detailed studies on the alterations produced in the amino acid sequence of a protein by mutations of the type discussed here.
The basic structure of proteins is quite simple: they are formed by hooking together in a chain discrete subunits called amino acids.
That the primary effect of gene mutation may be as simple as the substitution of a single amino acid by another and may lead to profound secondary changes in protein structure and properties has recently been strongly indicated by the work of Ingram on hemoglobin.
We know that if memory is destroyed in one part of the brain, it can be sometimes re-created on a different part of the brain. And once we can unravel that amino chain of chemicals that is responsible for memory, I see no reason why we can't unlock it and, essentially, wipe out what's there.
This seems highly likely, especially as it has been shown that in several systems mutations affecting the same amino acid are extremely near together on the genetic map.
Unfortunately it makes the unambiguous determination of triplets by these methods much more difficult than would be the case if there were only one triplet for each amino acid.
The balance of evidence both from the cell-free system and from the study of mutation, suggests that this does not occur at random, and that triplets coding the same amino acid may well be rather similar.
Human insulin differs from other mammalian types by having a different C-terminal amino acid on the B chain. The immunological difference between beef insulin and human insulin, which is presumably responsible for the antigenicity of the former in some human beings, is thus limited to very a small portion of the whole molecule.
The study of the amino acid sequence around the disulphide bonds of the immunoglobulins was my own short-cut to the understanding of antibody diversity.
The meaning of this observation is unclear, but it raises the unfortunate possibility of ambiguous triplets; that is, triplets which may code more than one amino acid. However one would certainly expect such triplets to be in a minority.
Ribosomes contain RNA, messenger RNA provides the information, transfer RNAs brings the amino acids; so the protein-making machinery is an RNA machinery, completely.
