Three‐dimensional structure of the quinoprotein methylamine dehydrogenase from Paracoccus denitrificans determined by molecular replacement at 2.8 Å resolution

Abstract

The three-dimensional structure of the quinoprotein methylamine dehydrogenase from Paracoccus dentrificans (PD-MADH) has been determined at 2.8 A resolution by the molecular replacement method combined with map averaging procedures, using data collected from an area detector. The structure of methylamine dehydrogenase from Thio-bacillus versutus, which contains an "X-ray" sequence, was used as the starting search model. MADH consists of 2 heavy (H) and 2 light (L) subunits related by a molecular 2-fold axis. The H subunit is folded into seven four-stranded beta segments, forming a disk-shaped structure, arranged with pseudo-7-fold symmetry. A 31-residue elongated tail exists at the N-terminus of the H subunit in MADH from T. versutus but is partially digested in this crystal form of MADH from P. denitrificans, leaving the H subunit about 18 residues shorter. Each L subunit contains 127 residues arranged into 10 beta-strands connected by turns. The active site of the enzyme is located in the L subunit and is accessible via a hydrophobic channel between the H and L subunits. The redox cofactor of MADH, tryptophan tryptophylquinone is highly unusual. It is formed from two covalently linked tryptophan side chains at positions 57 and 107 of the L subunit, one of which contains an orthoquinone.

Evolutionary Conservation and Predicted Structure of the Drosophila extra sex combs Repressor Protein

“…Likewise, 9 of the top 20 proteins with similarity to esc are ␤-propellers. The top-ranked match for G ␤ is the ␤-propeller protein methylamine dehydrogenase (9), and the top-ranked match for esc is the ␤-propeller galactose oxidase (17). These similarities indicate that it is reasonable to model esc protein as a ␤-propeller.…”

The biosynthesis of periplasmic electron transport proteins in methylotrophic bacteria

“…Methylamine is oxidized to formaldehyde by methylamine dehydrogenase, which was the first quinoprotein to have its structure determined by X-ray crystallography (Vellieux e t al., 1989 differs from that of methanol dehydrogenase, however, in having only a sevenfold radial symmetry and a centre occupied by amino acid residues and not by the prosthetic group (Vellieux et al ,1989 ;Chen et al , 1992b). This is not PQQ but another quinone structure, tryptophan tryptophylquinone (TTQ) (Fig.…”

Preliminary crystal structure studies of a ternary electron transfer complex between a quinoprotein, a blue copper protein, and a c‐type cytochrome

“…., 1983). The crystal structures of MADH from both Thiobucillus versutus (Vellieux et al, 1989) and P. denitrifcuns (Chen et al, 1992b) have been determined, based on an X-ray sequence for the former. The structure of the latter has recently been rebuilt using the DNA-derived amino acid sequence (Chistoserdov et al, 1992) and refined at 1.75 A resolution (Chen et al, in prep.…”