Evolution of feedback-inhibited beta /alpha barrel isoenzymes by gene duplication and a single mutation.
The betaalpha barrel is the common protein fold of numerous enzymes and was proposed recently to be the result of gene duplication and fusion of an ancient half-barrel. The initial enzyme of shikimate biosynthesis possesses the additional feature of feedback regulation. The crystal structure and kinetic studies on chimera and mutant proteins of yeast 3-deoxy-d-arabino-heptulosonate-7-phosphate (DAHP) synthase from Saccharomyces cerevisiae inhibited by phenylalanine (Aro3p) and DAHP synthase S. cerevisiae inhibited by tyrosine (Aro4p) give insight into important regions for regulation in the enzyme: The loop, which is connecting the two half-barrels, and structural elements added to the barrel are prerequisites for regulation and form a cavity on the N-terminal side of the betaalpha barrel. In the cavity of Aro4p at position 226 is a glycine residue, which is highly conserved in all other tyrosine-regulated DAHP synthases as well. Sequence alignments with phenylalanine-regulated DAHP synthases including Aro3p show a highly conserved serine residue at this position. An exchange of glycine to serine and vice versa leads to a complete change in the regulation pattern. Therefore the evolution of these differently feedback-inhibited isoenzymes required gene duplication and a single mutation within the internal extra element. Numerous additional amino acid substitutions present in the contemporary isoenzymes are irrelevant for regulation and occurred independently.
Hartmann
Markus
M
Institut für Mikrobiologie and Genetik and Abteilung für Strukturchemie, Georg August Universität, D-37077 Göttingen, Germany.
Schneider
Thomas R
TR
Pfeil
Andrea
A
Heinrich
Gabriele
G
Lipscomb
William N
WN
Braus
Gerhard H
GH
D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000737:chemistry*; D000483:Alleles; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D018360:Crystallography, X-Ray; D004798:Enzymes / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D012694:Serine / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry
D000596:Amino Acids; D004798:Enzymes; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D012694:Serine; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D005998:Glycine