Journal
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS
Volume 1814, Issue 6, Pages 810-816Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbapap.2010.11.001
Keywords
2/2 Hemoglobin; Truncated hemoglobin; Globin fold; Heme stabilization; Diatomic ligand recognition
Categories
Funding
- National Sciences and Engineering Research Council (NSERC) [46306-01, 250073]
- Fonds Quebecois de la Recherche sur la Nature et les Technologies (FQRNT) [78927]
- University of Milano
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Within the 2/2 hemoglobin sub-family, no group II 2/2Hbs from proteobacteria have been so far studied. Here we present the first structural characterization of a group II 2/2Hb from the soil and phytopathogenic bacterium Agrobacterium tumefaciens (At-2/2HbO). The crystal structure of ferric At-2/2HbO (reported at 2.1 angstrom resolution) shows the location of specific/unique heme distal site residues (e.g., His(42)CD1, a residue distinctive of proteobacteria group II 2/2Hbs) that surround a heme-liganded water molecule. A highly intertwined hydrogen-bonded network, involving residues Tyr(26)B10, His(42)CD1, Ser(49)E7, Trp(93)G8, and three distal site water molecules, stabilizes the heme-bound ligand. Such a structural organization suggests a path for diatomic ligand diffusion to/from the heme. Neither a similar distal site structuring effect nor the presence of distal site water molecules has been so far observed in group I and group III 2/2Hbs, thus adding new distinctive information to the complex picture of currently available 2/2Hb structural and functional data. This article is part of a Special Issue entitled: Protein Structure and Function in the Crystalline State. (C) 2010 Elsevier B.V. All rights reserved.
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