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Structural studies of domain movement in active-site mutants of porphobilinogen deaminase from Bacillus megaterium

DOI: 10.1107/S2053230X17015436 DOI Help

Authors: Jingxu Guo (University College London (UCL)) , Peter Erskine (University College London; Birkbeck, University of London) , Alun Coker (University College London) , Steve P. Wood (University College London) , Jonathan Cooper (University College London; Birkbeck, University of London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Crystallographica Section F Structural Biology Communications , VOL 73 , PAGES 612 - 620

State: Published (Approved)
Published: November 2017
Diamond Proposal Number(s): 8922

Abstract: The enzyme porphobilinogen deaminase (PBGD) is one of the key enzymes in tetrapyrrole biosynthesis. It catalyses the formation of a linear tetrapyrrole from four molecules of the substrate porphobilinogen (PBG). It has a dipyrromethane cofactor (DPM) in the active site which is covalently linked to a conserved cysteine residue through a thioether bridge. The substrate molecules are linked to the cofactor in a stepwise head-to-tail manner during the reaction, which is catalysed by a conserved aspartate residue: Asp82 in the B. megaterium enzyme. Three mutations have been made affecting Asp82 (D82A, D82E and D82N) and their crystal structures have been determined at resolutions of 2.7, 1.8 and 1.9 Å, respectively. These structures reveal that whilst the D82E mutant possesses the DPM cofactor, in the D82N and D82A mutants the cofactor is likely to be missing, incompletely assembled or disordered. Comparison of the mutant PBGD structures with that of the wild-type enzyme shows that there are significant domain movements and suggests that the enzyme adopts `open' and `closed' conformations, potentially in response to substrate binding.

Journal Keywords: protein crystallography; structural biology; porphobilinogen deaminase; Bacillus megaterium; tetrapyrrole biosynthesis

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I04-Macromolecular Crystallography

Added On: 06/11/2017 09:54

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