Membership mutation of the genetic code: loss of fitness by tryptophan.
Bacillus subtilis strain QB928, a tryptophan-auxotroph, was serially mutated to yield strain HR15. For QB928, tryptophan functioned as a competent amino acid and 4-fluorotryptophan as merely an inferior analogue. For HR15, these roles were reversed. The tryptophan/4-fluorotryptophan growth ratio decreased by a factor of 2 X 10(4) in the transition from QB928 to HR15.
D001412:Bacillus subtilis / Q000235:genetics; D005075:Biological Evolution; D005815:Genetic Code; D009154:Mutation; D013329:Structure-Activity Relationship; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000235:genetics*
C039390:4-fluorotryptophan; D014364:Tryptophan