3zh0

Publication Abstract from PubMed

Functional and structural properties of protoglobin from Methanosarcina acetivorans, whose Cys(E20)101 residue was mutated to Ser (MaPgb*), and of mutants missing either the first 20N-terminal amino acids (MaPgb*-DeltaN20 mutant), or the first 33N-terminal amino acids [N-terminal loop of 20 amino acids and a 13-residue Z-helix, preceding the globin fold A-helix; (MaPgb*-DeltaN20Z mutant)] have been investigated. In keeping with the MaPgb*-DeltaN20 mutant crystal structure, here reported at 2.0A resolution, which shows an increased exposure of the haem propionates to the solvent, the analysis of ligand binding kinetics highlights high accessibility of ligands to the haem pocket in ferric MaPgb*-DeltaN20. CO binding to ferrous MaPgb*-DeltaN20 displays a marked biphasic behavior, with a fast binding process close to that observed in MaPgb* and a slow carbonylation process, characterized by a rate-limiting step. Conversely, removal of the first 33 residues induces a substantial perturbation of the overall MaPgb* structure, with loss of alpha-helical content and potential partial collapse of the protein chain. As such, ligand binding kinetics are characterized by very slow rates that are independent of ligand concentration, this being indicative of a high energy barrier for ligand access to the haem, possibly due to localized misfolding. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.

Functional and structural role of the N-terminal extension in Methanosarcina acetivorans protoglobin.,Ciaccio C, Pesce A, Tundo GR, Tilleman L, Bertolacci L, Dewilde S, Moens L, Ascenzi P, Bolognesi M, Nardini M, Coletta M Biochim Biophys Acta. 2013 Feb 25. pii: S1570-9639(13)00089-7. doi:, 10.1016/j.bbapap.2013.02.026. PMID:23485914^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.