Myoglobin and mitochondria: Oxymyoglobin interacts with mitochondrial membrane during deoxygenation

Abstract

The rates of oxygen uptake by rat liver mitochondria (MC) (native coupled, freshly frozen, and uncoupled by FCCP) have been measured polarographically in the absence (V(0)) or presence (V(1)) of 0.11-0.25 mM sperm whale MbO2. Under the same standard conditions, the rate of sperm whale MbO2 deoxygenation (V(2)) has been studied spectrophotometrically in the presence of respiring MC. For freshly frozen MC, the dependence of V(1) and V(2) on the overall charge of MbO2 has been investigated at pH 5.6-7.6, and the influence of other differently charged proteins (apomyoglobin, egg lysozyme, lactalbumin, and BSA) has been studied at pH 7.4. It is shown that the rate of mitochondrial respiration in the presence of MbO2 increases by 10-30% (V(1) > V(0)). No myoglobin effect is observed for FCCP-uncoupled MC (V(max) does not change). The rate of MbO2 deoxygenation is equal to the rate of oxygen uptake by mitochondria (V(2)/V(1) ~ 1 at pH 7.2-7.5). At varying pH < 7.2, the V(2) values become markedly higher than V(1), evidently due to the increased MbO2 positive charge and its stronger interaction with negatively charged mitochondrial membrane. At pH 7.4, on the contrary, V(2) is twice lower than V(1) in the case of negatively charged CM-MbO2 (pI 5.2), which has carboxymethylated histidines. Positively charged lysozyme (pI 11) strongly inhibits MbO2 deoxygenation (V(2)) without affecting oxygen uptake by MC (V(0) and V(1)). At the same time, apomyoglobin (pI 8.5), which is structurally very similar to the holoprotein, and both negatively charged lactalbumin (pI 4.4) and BSA (pI 4.7) have no substantial influence on V(2) and V(1). The MC membrane evidently has no specific sites for the interaction with myoglobin. Rather, the protein contacts with phospholipids of the outer membrane during MbO2 deoxygenation, and electrostatic interactions are of great importance for this process.

Novel Molecular Interactions of Acylcarnitines and Fatty Acids with Myoglobin

“…through site-directed mutagenesis). Interestingly, recent studies indicate that oxy-Mb interacts with mitochondria in the muscle cells, initiating a conformational change in the oxy-Mb during the release of oxygen (40,41). These results must be taken into account in future studies of the retention of fatty acids or acylcarnitines when bound to oxy-Mb that may simultaneously release both oxygen and lipids to the mitochondria.…”

Myoglobin and the regulation of mitochondrial respiratory chain complex IV

“…Because previous studies have shown mitochondrial localization of Mb (Postnikova et al 2009) and interaction with COX IV, a subunit comprising respiratory complex IV (Yamada et al 2013), a new hypothesis proposing interaction between mitochondrial protein and Mb (Mito-Mb) has emerged, which identifies the underlying mechanisms for a direct role for Mb in interacting with complex IV to modulate mitochondrial respiration. Therefore, we hypothesized that the direct Mb interaction in the mitochondria (mito-Mb) improves complex IV activity.…”

Myoglobin and Mitochondria: How Does The “Oxygen Store” Work?

“…We first showed that O 2 release from MbO 2 at physiological p O2 values proceeds only upon direct contact of the protein with mitochondria [16,17]. If respiring mitochondria are separated from MbO 2 solution by a semipermeable membrane (mitochondria are inside a closed dialysis bag), no MbO 2 deoxygenation occurs even at near-zero O 2 concentration ( Figure 1a).…”

“…The rate of oxygen release from MbO 2 in the presence of mitochondria (V 2 ) measured spectrophotometrically ( Figure 1b) is constant during the entire period of the oxy-deoxy transition (τ tr ) and does not depend on MbO 2 concentration (the 0-th order in myoglobin). Indeed, no reaction rate changes are observed with increasing MbO 2 concentration more than twofold (Table 1) [16,17]. Lowering the reaction order in comparison with 1st-order reaction of MbO 2 deoxygenation in solution (Equation 1) is inherent for different processes with participation of membranes [18].…”

“…Competitive effect of different proteins on deoxygenation rate of MbO 2 in suspension of mitochondria [17].…”