Cooperative oxygen binding in beta-semihemoglobins caused by a chemical modification in the alpha1beta1 interface.

A beta-semihemoglobin is an alpha-beta dimer of hemoglobin (Hb) in which the beta-subunit carries heme, while the alpha-subunit is heme-less, in apo form. It is characterised by displaying a high affinity for oxygen, and absence of cooperative binding of oxygen. We have modified chemically the residue beta112Cys (G14), located adjacent to the alpha1beta1 interface, and studied the impact of such a modification on the oligomeric state and oxygenation properties of the derivatives.

Tracing whale myoglobin evolution by resurrecting ancient proteins.

Extant cetaceans, such as sperm whale, acquired the great ability to dive into the ocean depths during the evolution from their terrestrial ancestor that lived about 50 million years ago. Myoglobin (Mb) is highly concentrated in the myocytes of diving animals, in comparison with those of land animals, and is thought to play a crucial role in their adaptation as the molecular aqualung. Here, we resurrected ancestral whale Mbs, which are from the common ancestor between toothed and baleen whales (Basilosaurus), and from a further common quadrupedal ancestor between whale and hippopotamus (Pakicetus).

Change of the isoelectric point of hemoglobin at the air/water interface probed by the orientational flip-flop of water molecules.

Elucidation of the molecular mechanisms of protein adsorption is of essential importance for further development of biotechnology. Here, we use interface-selective nonlinear vibrational spectroscopy to investigate protein charge at the air/water interface by probing the orientation of interfacial water molecules. We measured the Im χ spectra of hemoglobin, myoglobin, serum albumin and lysozyme at the air/water interface in the CH and OH stretching regions using heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy, and we deduced the isoelectric point of the protein by monitoring the orientational flip-flop of water molecules at the interface.

A new paramagnetic intermediate formed during the reaction of nitrite with deoxyhemoglobin.

The reduction of nitrite by deoxygenated hemoglobin chains has been implicated in red cell-induced vasodilation, although the mechanism for this process has not been established. We have previously demonstrated that the reaction of nitrite with deoxyhemoglobin produces a hybrid intermediate with properties of Hb(II)NO(+) and Hb(III)NO that builds up during the reaction retaining potential NO bioactivity. To explain the unexpected stability of this intermediate, which prevents NO release from the Hb(III)NO component, we had implicated the transfer of an electron from the β-93 thiol to NO(+) producing ·SHb(II)NO.

T-quaternary structure of oxy human adult hemoglobin in the presence of two allosteric effectors, L35 and IHP.

The cooperative O(2)-binding of hemoglobin (Hb) have been assumed to correlate to change in the quaternary structures of Hb: T(deoxy)- and R(oxy)-quaternary structures, having low and high O(2)-affinities, respectively. Heterotropic allosteric effectors have been shown to interact not only with deoxy- but also oxy-Hbs causing significant reduction in their O(2)-affinities and the modulation of cooperativity. In the presence of two potent effectors, L35 and inositol hexaphosphate (IHP) at pH 6.