Novel fluorescence membrane fusion assays reveal GTP-dependent fusogenic properties of outer mitochondrial membrane-derived proteins.

We have shown that fusion of small unilamellar vesicles (SUV) with outer mitochondrial membranes occurs at physiological pH [Cortese et al., 1991, J. Cell Biol.

Multiple conformations of physiological membrane-bound cytochrome c.

One-tenth of cytochrome c (cyt c) remains bound to the inner mitochondrial membrane (IMM) at physiological ionic strength (I; i.e. , I approximately 150 mM), exhibiting decreased electron transport (ET) activity.

Persistence of cytochrome c binding to membranes at physiological mitochondrial intermembrane space ionic strength.

We have shown that cytochrome c (cyt c) diffuses primarily in three dimensions in the intermembrane space (IMS) of intact mitochondria at physiological ionic strength (I). Recently, we found that a small percentage (11.2 +/- 2.

Motional dynamics of functional cytochrome c delivered by low pH fusion into the intermembrane space of intact mitochondria.

We have investigated the motional dynamics of cytochrome c in the intact, functional rat liver mitochondrion. To do this, functional, FITC-cytochrome c (fluorescein isothiocyanate monoderivatized cytochrome c) was incorporated into the intermembrane space (IMS) of intact mitochondria through encapsulation of cytochrome c into asolectin liposomes followed by low pH-induced fusion of the liposomes with the outer membranes of the mitochondria. A cytochrome c controlled enrichment of between 15%-50% (1800-7200 molecules incorporated per mitochondrion) was obtained.

The ionic strength of the intermembrane space of intact mitochondria is not affected by the pH or volume of the intermembrane space.

Ionic strength affects the electron transport activity of cytochrome c through its electrostatic interactions with redox partners and membrane lipids. We previously reported (Cortese, J.D.