Structural basis of the hydride transfer mechanism in [F.sub.420]-dependent methylenetetrahydromethanopterin dehydrogenase

The structural characterization of methylenetetrahydromethanopterin Mtd-methylene-[H.sub.4]MPT, Mtd-methenyl-[[H.sub.4]MPT.sup.+], and the Mtd-methenyl-[[H.sub.4]MPT.sup.+]-[F.sub.420][H.sub.2] complexes of Methanopyrus kandleri at 2.1, 2.0, and 1.8 [Angstrom] resolution, respectively is reported. The polypeptide scaffold did not reveal any significant conformational change upon binding of the bulky substrates but in turn changed 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.