Myoglobin: Oxygen Depot or Oxygen Transporter to Mitochondria? A Novel Mechanism of Myoglobin Deoxygenation in Cells (review).

In this review, we shortly summarize the data of our studies (and also corresponding studies of other authors) on the new mechanism of myoglobin (Mb) deoxygenation in a cell, according to which Mb acts as an oxygen transporter, and its affinity for the ligand, like in other transporting proteins, is regulated by the interaction with the target, in our case, mitochondria (Mch). We firstly found that contrary to previously formulated and commonly accepted concepts, oxymyoglobin (MbO) deoxygenation occurs only via interaction of the protein with respiring mitochondria (low p values are necessary but not sufficient for this process to proceed). Detailed studies of the mechanism of Mb-Mch interaction by various physicochemical methods using natural and artificial bilayer phospholipid membranes showed that: (i) the rate of MbO deoxygenation in the presence of respiring Mch fully coincides with the rate of O2 uptake by mitochondria from a solution irrespectively of their state (native coupled, freshly frozen, or FCCP-uncoupled), i.

Hemoglobin and Myoglobin as Reducing Agents in Biological Systems. Redox Reactions of Globins with Copper and Iron Salts and Complexes.

In addition to reversible O2 binding, respiratory proteins of the globin family, hemoglobin (Hb) and myoglobin (Mb), participate in redox reactions with various metal complexes, including biologically significant ones, such as those of copper and iron. HbO and MbO are present in cells in large amounts and, as redox agents, can contribute to maintaining cell redox state and resisting oxidative stress. Divalent copper complexes with high redox potentials (E, 200-600 mV) and high stability constants, such as [Cu(phen)], [Cu(dmphen)], and CuDTA oxidize ferrous heme proteins by the simple outer-sphere electron transfer mechanism through overlapping π-orbitals of the heme and the copper complex.

Effect of artificial and natural phospholipid membranes on rate of sperm whale oxymyoglobin autooxidation.

We were the first to show that MbO2 deoxygenation in the cell occurs only upon interaction of myoglobin with mitochondrial membrane, which must be accompanied by changes in the heme cavity conformation of the protein and its affinity for the ligand. Under aerobic conditions, some changes in the equilibrium O2 dissociation constant (Kdis) can be detected by changes of the rate of MbO2 autooxidation, i.e.

Fluorescence studies on the interaction of myoglobin with mitochondria.

To determine the nature and characteristic parameters of the myoglobin-mitochondrion interaction during oxymyoglobin (MbO(2)) deoxygenation in the cell, we studied the quenching of the intrinsic mitochondrial flavin and tryptophan fluorescence by different liganded myoglobins in the pH range of 6-8, as well as the quenching of the fluorescence of the membrane probes 1,8-ANS and merocyanine 540 (M 540) embedded into the mitochondrial membrane. Physiologically active MbO(2) and oxidized metmyoglobin (metMb), which are unable to bind oxygen, were used as the quenchers. The absence of quenching of flavin and tryptophan fluorescence implies that myoglobin does not form quenching complexes with either electron transport chain proteins of the inner mitochondrial membrane or with outer membrane proteins.

[Study of the interaction of myoglobin with lipid bilayer membranes by potentiodynamic method].

For modeling the interaction of myoglobin with mitochondrial membranes, the adsorption of different ligand forms, the physiologically active reduced MbO2 and inactive oxidized met-Mb, on one of the surfaces of artificial bilayer lipid membrane (BLM) was studied using potentiodynamic technique known as the "capacity minimization" method. As mitochondrial membranes are negatively charged, BLM from the negatively charged palmitoyl-2-oleil-phosphatidyl glycerol (POPG) and neutral soybean phosphatidylcholine (lecithin) were used. It is shown that both myoglobins strongly interact with BLM in the pH range 6-8.