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 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.
Related Citations:
Pyruvoyl-Dependent Histidine Decarboxylase: Active Site Structure and Mechanistic Analysis Gallagher, T., Snell, E.E., Hackert, M.L. (1989) J Biol Chem 264: 12737
Structure Determination of Histidine Decarboxylase from Lactobacillus 30A at 3.0 Angstroms Resolution Parks, E.H., Ernst, S.R., Hamlin, R., Xuong, N.H., Hackert, M.L. (1985) J Mol Biol 182: 455
The Molecular Symmetry of Histidine Decarboxylase and Prohistidine Decarboxylase by Rotation Function Analysis Parks, E.H., Clinger, K., Hackert, M.L. (1983) Acta Crystallogr B 39: 490
Crystallization and Subunit Structure of Histidine Decarboxylase from Lactobacillus 30A Hackert, M.L., Meador, W.E., Oliver, R.M., Salmon, J.B., Rescei, P.A., Snell, E.E. (1981) J Biol Chem 256: 687
Organizational Affiliation:
Clayton Foundation Biochemical Institute, Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
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