Refined structure of the pyruvoyl-dependent histidine decarboxylase from Lactobacillus 30a.
The crystal structure of the pyruvoyl-dependent histidine decarboxylase from Lactobacillus 30a has been refined to an R-value of 0.15 (for the 5.0 to 2.5 A resolution shell) and 0.17 (for the 10.0 to 2.5 A resolution shell). A description of the overall structure is presented, focusing on secondary structure and subunit association. The enzyme is a hexamer of alpha beta subunits. Separate alpha and beta-chains arise from an autocatalytic cleavage reaction between two serine residues, which results in the pyruvoyl cofactor. The central core of the alpha beta subunit is a beta-sandwich which consists of two face-to-face three-stranded antiparallel beta-sheets, flanked by alpha-helices on each side. The beta-sandwich creates a stable fold that allows conformational strain to be introduced across an internal cleavage region between the alpha and beta chains and places the pyruvoyl cofactor in a position for efficient electron withdrawal from the substrate. Three alpha beta subunits are related by a molecular three-fold symmetry axis to form a trimer whose interfaces have complementary surfaces and extensive molecular interactions. Each of the interfaces contains an active site and a solvent channel that leads from the active site to the exterior of the molecule. The trimers are related by a crystallographic two-fold symmetry axis to form the hexamer with an overall dumbbell shape. The interface between trimers has few molecular interactions.
Gallagher
T
T
Clayton Foundation Biochemical Institute, Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
Rozwarski
D A
DA
Ernst
S R
SR
Hackert
M L
ML
D000595:Amino Acid Sequence; D006640:Histidine Decarboxylase / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D007778:Lactobacillus / Q000201:enzymology*; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011773:Pyruvates / Q000378:metabolism; D014961:X-Ray Diffraction / Q000379:methods
D046911:Macromolecular Substances; D011773:Pyruvates; D006640:Histidine Decarboxylase