The Crystal Structure of [Fe]-Hydrogenase Reveals the Geometry of the Active Site
Seigo Shima,1*
Oliver Pilak,1*
Sonja Vogt,1
Michael Schick,1
Marco S. Stagni,2
Wolfram Meyer-Klaucke,2
Eberhard Warkentin,3
Rudolf K. Thauer,1
Ulrich Ermler3
Biological formation and consumption of molecular hydrogen (H
2)
are catalyzed by hydrogenases, of which three phylogenetically
unrelated types are known: [NiFe]-hydrogenases, [FeFe]-hydrogenases,
and [Fe]-hydrogenase. We present a crystal structure of [Fe]-hydrogenase
at 1.75 angstrom resolution, showing a mononuclear iron coordinated
by the sulfur of cysteine 176, two carbon monoxide (CO) molecules,
and the sp
2-hybridized nitrogen of a 2-pyridinol compound with
back-bonding properties similar to those of cyanide. The three-dimensional
arrangement of the ligands is similar to that of thiolate, CO,
and cyanide ligated to the low-spin iron in binuclear [NiFe]-
and [FeFe]-hydrogenases, although the enzymes have evolved independently
and the CO and cyanide ligands are not found in any other metalloenzyme.
The related iron ligation pattern of hydrogenases exemplifies
convergent evolution and presumably plays an essential role
in H
2 activation. This finding may stimulate the ongoing synthesis
of catalysts that could substitute for platinum in applications
such as fuel cells.
2 EMBL Hamburg, Notkestr. 85, D-22603 Hamburg, Germany.
3 Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, D-60438 Frankfurt/Main, Germany.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: ulermler{at}mpibp-frankfurt.mpg.de; shima{at}mpi-marburg.mpg.de
