Functional and structural roles of the N-terminal extension in Methanosarcina acetivorans protoglobin
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- 作者：Chiara Ciaccio ; Aless ; ra Pesce ; Grazia R. Tundo ; Lesley Tilleman ; Laura Bertolacci ; Sylvia Dewilde ; Luc Moens ; Paolo Ascenzi ; Martino Bolognesi ; Marco Nardini ; Massimo Coletta
- 关键词：Pgb ; protoglobin ; GCS ; globin coupled sensors ; MaPgb ; Methanosarcina acetivorans protoglobin ; MaPgb* ; Methanosarcina acetivorans protoglobin whose Cys(101)E20 is replaced by Ser ; Hb ; hemoglobin ; Mb ; myoglobin ; MaPgb*-¦¤N20 ; Methanosarcina acetivorans prot
- 刊名：Biochimica et Biophysica Acta - Proteins and Proteomics
- 出版年：2013
- 出版时间：September, 2013
- 年：2013
- 卷：1834
- 期：9
- 页码：1813-1823
- 全文大小：1764 K
文摘
Functional and structural properties of protoglobin from Methanosarcina acetivorans, whose Cys(101)E20 residue was mutated to Ser (MaPgb*), and of mutants missing either the first 20 N-terminal amino acids (MaPgb*-¦¤N20 mutant), or the first 33 N-terminal amino acids [N-terminal loop of 20 amino acids and a 13-residue Z-helix, preceding the globin fold A-helix; (MaPgb*-¦¤N20Z mutant)] have been investigated. In keeping with the MaPgb*-¦¤N20 mutant crystal structure, here reported at 2.0 ? 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*-¦¤N20. CO binding to ferrous MaPgb*-¦¤N20 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 ¦Á-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.