Myoglobin and Mitochondria: Oxymyoglobin Interacts with Mitochondrial Membrane during Deoxygenation

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G. B. Postnikova^*, S. V. Tselikova, and E. A. Shekhovtsova

Institute of Cell Biophysics, Russian Academy of Sciences, ul. Institutskaya 3, 142290 Pushchino, Moscow Region, Russia; fax: (496) 733-0509; E-mail: gbpost@mail.ru

^* To whom correspondence should be addressed.

Received April 28, 2008; Revision received April 10, 2009

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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 (V₀) or presence (V₁) of 0.11-0.25 mM sperm whale MbO₂. Under the same standard conditions, the rate of sperm whale MbO₂ deoxygenation (V₂) has been studied spectrophotometrically in the presence of respiring MC. For freshly frozen MC, the dependence of V₁ and V₂ 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% (V₁ > V₀). 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 (V₂/V₁ ~ 1 at pH 7.2-7.5). At varying pH < 7.2, the V₂ values become markedly higher than V₁, evidently due to the increased MbO₂ positive charge and its stronger interaction with negatively charged mitochondrial membrane. At pH 7.4, on the contrary, V₂ is twice lower than V₁ in the case of negatively charged CM-MbO₂ (pI 5.2), which has carboxymethylated histidines. Positively charged lysozyme (pI 11) strongly inhibits MbO₂ deoxygenation (V₂) without affecting oxygen uptake by MC (V₀ and V₁). 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 V₂ and V₁. 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.

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KEY WORDS: mitochondria, myoglobin, deoxygenation, membrane

DOI: 10.1134/S0006297909110054

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