Crystal structure of ethylbenzene dehydrogenase from Aromatoleum aromaticum.
Anaerobic degradation of hydrocarbons was discovered a decade ago, and ethylbenzene dehydrogenase was one of the first characterized enzymes involved. The structure of the soluble periplasmic 165 kDa enzyme was established at 1.88 A resolution. It is a heterotrimer. The alpha subunit contains the catalytic center with a molybdenum held by two molybdopterin-guanine dinucleotides, one with an open pyran ring, and an iron-sulfur cluster with a histidine ligand. During catalysis, electrons produced by substrate oxidation are transferred to a heme in the gamma subunit and then presumably to a separate cytochrome involved in nitrate respiration. The beta subunit contains four iron-sulfur clusters and is structurally related to ferredoxins. The gamma subunit is the first known protein with a methionine and a lysine as axial heme ligands. The catalytic product was modeled into the active center, showing the reaction geometry. A mechanism consistent with activity and inhibition data of ethylbenzene-related compounds is proposed.
Kloer
Daniel P
DP
Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstr. 21, D-79104 Freiburg im Breisgau, Germany.
Hagel
Corina
C
Heider
Johann
J
Schulz
Georg E
GE
D003461:Crystallography; D008958:Models, Molecular; D010088:Oxidoreductases / Q000737:chemistry*; D011487:Protein Conformation; D020560:Proteobacteria / Q000201:enzymology*
D010088:Oxidoreductases; C121602:ethylbenzene dehydrogenase