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High Resolution Crystal Structures of the Cerebratulus lacteus Mini-Hb in the Unligated and Carbomonoxy States
Department of Biomedical Sciences, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
Department of Physics, University of Genova, Via Dodecaneso 33, I-16146 Genova, Italy
Dipartimento di BioScienze, Università degli Studi di Milano, Via Celoria 26, I-20133 Milano, Italy
* Authors to whom correspondence should be addressed.
Received: 31 May 2012; in revised form: 14 June 2012 / Accepted: 15 June 2012 / Published: 28 June 2012
Abstract: The nerve tissue mini-hemoglobin from Cerebratulus lacteus (CerHb) displays an essential globin fold hosting a protein matrix tunnel held to allow traffic of small ligands to and from the heme. CerHb heme pocket hosts the distal TyrB10/GlnE7 pair, normally linked to low rates of O2 dissociation and ultra-high O2 affinity. However, CerHb affinity for O2 is similar to that of mammalian myoglobins, due to a dynamic equilibrium between high and low affinity states driven by the ability of ThrE11 to orient the TyrB10 OH group relative to the heme ligand. We present here the high resolution crystal structures of CerHb in the unligated and carbomonoxy states. Although CO binds to the heme with an orientation different from the O2 ligand, the overall binding schemes for CO and O2 are essentially the same, both ligands being stabilized through a network of hydrogen bonds based on TyrB10, GlnE7, and ThrE11. No dramatic protein structural changes are needed to support binding of the ligands, which can freely reach the heme distal site through the apolar tunnel. A lack of main conformational changes between the heme-unligated and -ligated states grants stability to the folded mini-Hb and is a prerequisite for fast ligand diffusion to/from the heme.
Keywords: nerve globin; crystal structure; heme reactivity; carbon monoxide; protein matrix tunnel
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MDPI and ACS Style
Germani, F.; Pesce, A.; Venturini, A.; Moens, L.; Bolognesi, M.; Dewilde, S.; Nardini, M. High Resolution Crystal Structures of the Cerebratulus lacteus Mini-Hb in the Unligated and Carbomonoxy States. Int. J. Mol. Sci. 2012, 13, 8025-8037.
Germani F, Pesce A, Venturini A, Moens L, Bolognesi M, Dewilde S, Nardini M. High Resolution Crystal Structures of the Cerebratulus lacteus Mini-Hb in the Unligated and Carbomonoxy States. International Journal of Molecular Sciences. 2012; 13(7):8025-8037.
Germani, Francesca; Pesce, Alessandra; Venturini, Andrea; Moens, Luc; Bolognesi, Martino; Dewilde, Sylvia; Nardini, Marco. 2012. "High Resolution Crystal Structures of the Cerebratulus lacteus Mini-Hb in the Unligated and Carbomonoxy States." Int. J. Mol. Sci. 13, no. 7: 8025-8037.