Chorismate

1
Variations in among TrpG and TrpD among the
Proteobacteria
Mary Ann Wagner, Craig Laufer, Michelle Lum

Trptophan biosynthetic pathway

TrpE TrpG
TrpB TrpA
TrpD
TrpC/F
TrpC/F
1-(2-Carboxy-phenylamino)-1-deoxy-D-ribulose
5-phosphate
N-(5-Phospho-B-D-ribosyl)-anthranilate
(3-Indolyl)-glycerol phosphate
Chorismate
Antranilate
L-Trptophan
TrpE anthranilate synthase component I TrpG
anthranilate synthase component II TrpD
anthranilate phosphoribosyltransferase TrpC/F
bifunctional indole-3-glycerol phosphate synthase/
phosphoribosylanthranilate isomerase TrpB
tryptophan synthase subunit beta TrpA tryptophan
synthase subunit alpha
Operon structure in Yersinia
16S rRNA tree
TrpG and TrpD are fused in E. coli, Citrobacter,
Klebsiella, Enterobacter, Salmonella, but not
Yersinia and Serratia
Klebsiella
Serratia
UAA stop
Conclusion
At some point in the evolution of the
Enterobacteriaceae there was a fusion event due
to mutation of a stop codon. However, it appears
Serratia may have had a back mutation such that
the two genes became unfused again.