title: Structure of uracil-DNA glycosylase from Mycobacterium tuberculosis: insights into interactions with ligands.
abstract: Uracil N-glycosylase (Ung) is the most thoroughly studied of the group of uracil DNA-glycosylase (UDG) enzymes that catalyse the first step in the uracil excision-repair pathway. The overall structure of the enzyme from Mycobacterium tuberculosis is essentially the same as that of the enzyme from other sources. However, differences exist in the N- and C-terminal stretches and some catalytic loops. Comparison with appropriate structures indicate that the two-domain enzyme closes slightly when binding to DNA, while it opens slightly when binding to the proteinaceous inhibitor Ugi. The structural changes in the catalytic loops on complexation reflect the special features of their structure in the mycobacterial protein. A comparative analysis of available sequences of the enzyme from different sources indicates high conservation of amino-acid residues in the catalytic loops. The uracil-binding pocket in the structure is occupied by a citrate ion. The interactions of the citrate ion with the protein mimic those of uracil, in addition to providing insights into other possible interactions that inhibitors could be involved in.
authors.affiliation: Molecular Biophysics Unit, Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: Prem Singh
authors.initials: PS
authors.lastname: Kaushal
authors.forename: Ramappa K
authors.initials: RK
authors.lastname: Talawar
authors.forename: Umesh
authors.initials: U
authors.lastname: Varshney
authors.forename: M
authors.initials: M
authors.lastname: Vijayan
mesh_terms: D019343:Citric Acid / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D040681:Structural Homology, Protein; D051981:Uracil-DNA Glycosidase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008024:Ligands; D019343:Citric Acid; D051981:Uracil-DNA Glycosidase