High resolution crystal structure of deoxy hemoglobin from Trematomus bernacchii at different pH values: The role of histidine residues in modulating the strength of the root effect
High resolution crystal structure of deoxy hemoglobin from Trematomus bernacchii at different pH values: The role of histidine residues in modulating the strength of the root effect(620 views) Mazzarella L, Vergara A, Vitagliano L, Merlino A, Bonomi G, Scala S, Verde C, Di Prisco G
Proteins (ISSN: 0887-3585, 1097-0134, 1097-0134electronic), 2006 Nov 1; 65(2): 490-498.
Dipartimento di Chimica, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, via Cinthia, I-80126 Naples, Italy
Istituto di Biostrutture e Bioimmagini, CNR, via Mezzocannone 6, I-80134 Naples, Italy
Istituto di Biochimica delle Proteine, CNR, via Pietro Castellino 111, I-80131 Naples, Italy
References: Not available.
High resolution crystal structure of deoxy hemoglobin from Trematomus bernacchii at different pH values: The role of histidine residues in modulating the strength of the root effect
The Root effect is a widespread property in fish hemoglobins (Hbs) that produces a drastic reduction of cooperativity and oxygen-binding ability at acidic pH. Here, we report the high-resolution structure of the deoxy form of Hb isolated from the Antarctic fish Trematomus bernacchii (HbTb) crystallized at pH 6.2 and 8.4. The structure at acidic pH has been previously determined at a moderate resolution (Ito et al., J Mol Biol 1995;250:648-658). Our results provide a clear picture of the events occurring upon the pH increase from 6.2 to 8.4, observed within a practically unchanged crystal environment. In particular, at pH 8.4, the interaspartic hydrogen bond at the alpha(1)beta(2) interface is partially broken, suggesting a pK(a) close to 8.4 for Asp95 alpha. In addition, a detailed survey of the histidine modifications, caused by the change in pH, also indicates that at least three hot regions of the molecule are modified (E beta helix, C beta-tail, CD alpha corner) and can be considered to be involved at various levels in the release of the Root protons. Most importantly, at the CD alpha corner, the break of the salt bridge Asp48 alpha-His55 alpha allows us to describe a detailed mechanism that transmits the modification from the CD alpha corner far to the a heme. More generally, the results shed light on the role played by the histidine residues in modulating the strength of the Root effect and also support the emerging idea that the structural determinants, at least for a part of the Root effect, are specific of each Hb endowed with this property.
High resolution crystal structure of deoxy hemoglobin from Trematomus bernacchii at different pH values: The role of histidine residues in modulating the strength of the root effect
High resolution crystal structure of deoxy hemoglobin from Trematomus bernacchii at different pH values: The role of histidine residues in modulating the strength of the root effect
Cusanno F, Cisbani E, Colilli S, Fratoni R, Garibaldi F, Giuliani F, Gricia M, Lucentini M, Magliozzi ML, Santarivenere F, Torrioli S, Cinti MN, Pani R, Pellegrini R, Simonetti G, Schillaci O, Del Vecchio S, Salvatore M, Majewski S, De Vincentis G, Scopinaro F * Results of clinical trials with SPEM(611 views) Nucl Instrum Methods Phys Res Sect A, 2007 Feb 1; 497(1): 46-50. Impact Factor:3.221 ViewExport to BibTeXExport to EndNote