When does a mutant stop being a mutant, and start being a new wild type?
A large part of our project involved generating a number of mutations in the distinct blue chromoprotein, amilCP, using error-prone PCR. We were searching for mutants that still produced the trademark blue colour of the wild type form, but perhaps expressed this colour more boldly, more quickly, or reversibly.
Instead, we succeeded in generating a range of mutant strains with a single or small number of base changes that caused the protein to express a different colour. Mint green, pale pink, and mauve were all samples we collected and sequenced to identify the mutation that caused the colour change, before performing spectral analysis on them to characterise their optical properties.
During this characterisation process, we began to discuss what to call these mutants. Is it appropriate to refer to a protein that turns pink as amilCP, a chromoprotein that is by definition or distinction blue?
We began to think about where the line can be drawn between a mutant strain and a new native strain. These mutant strains are being submitted to the iGEM parts registry as improvements of amilCP. In a major way, these mutants are a great improvement to the registry as they double the number of colours of chromoproteins available. They are derivations of amilCP, and thus cannot be discounted as relatives of this blue chromoprotein. And yet, they are not blue.
To investigate this phenomenon more, a sequence comparison on all the mutant colour strains and the wild type strain was conducted. As shown below, the sequences are identical with the exception of single nucleotide changes. Is it fair to say that for two different strains of a protein can be referred to as different proteins entirely if at least 1% of their sequences are different? Is it responsible to choose an arbitrary value in such way?
Is it correct to call these rainbow chromoproteins amilCP mutants, or should they stand alone as their own wild type species? Or are they both?
What do you think?