Structural basis of the hydride transfer mechanism in F(420)-dependent methylenetetrahydromethanopterin dehydrogenase.
F(420)-dependent methylenetetrahydromethanopterin (methylene-H(4)MPT) dehydrogenase (Mtd) of Methanopyrus kandleri is an enzyme of the methanogenic energy metabolism that catalyzes the reversible hydride transfer between methenyl-H(4)MPT(+) and methylene-H(4)MPT using coenzyme F(420) as hydride carrier. We determined the structures of the Mtd-methylene-H(4)MPT, Mtd-methenyl-H(4)MPT(+), and the Mtd-methenyl-H(4)MPT(+)-F(420)H(2) complexes at 2.1, 2.0, and 1.8 A resolution, respectively. The pterin-imidazolidine-phenyl ring system is present in a new extended but not planar conformation which is virtually identical in methenyl-H(4)MPT(+) and methylene-H(4)MPT at the current resolution. Both substrates methenyl-H(4)MPT(+) and F(420)H(2) bind in a face to face arrangement to an active site cleft, thereby ensuring a direct hydride transfer between their C14a and C5 atoms, respectively. The polypeptide scaffold does not reveal any significant conformational change upon binding of the bulky substrates but in turn changes the conformations of the substrate rings either to avoid clashes between certain ring atoms or to adjust the rings involved in hydride transfer for providing an optimal catalytic efficiency.
Ceh
Katharina
K
Max-Planck-Institut fur Biophysik, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany.
Demmer
Ulrike
U
Warkentin
Eberhard
E
Moll
Johanna
J
Thauer
Rudolf K
RK
Shima
Seigo
S
Ermler
Ulrich
U
D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D019605:Euryarchaeota / Q000201:enzymology / Q000378:metabolism; D008958:Models, Molecular; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D000587:Oxidoreductases Acting on CH-NH Group Donors; C047126:methylenetetrahydromethanopterin dehydrogenase