Comparative studies on mitochondrial coupling factor B and FB. |
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Authors: | S Sharma D R Sanadi |
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Institution: | 1. Department of Cell Physiology, Boston Biomedical Research Institute 20 Staniford Street, Boston, Massachusetts 02114 USA;2. Department of Biological Chemistry, Harvard Medical School USA |
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Abstract: | Beef heart mitochondrial protein factor FB Higashiyama , Biochemistry , 4117–4121 (1975)] was purified and its properties were compared with those of coupling factor B. Both proteins stimulated ATP-driven NAD+ reduction in ammonia and EDTA-treated (AE-) submitochondrial particles, but the extent of stimulation (maximum activity of particles) was very low with FB. FB was found to be ineffective in stimulating Pi-ATP exchange in either AE-particles or reconstituted oligomycin-sensitive ATPase vesicles. Furthermore, FB failed to stimulate ATP-driven NAD+ reduction activity of AE-particles in the presence of saturating amounts of dithiothreitol (DTT). DTT alone stimulates the particle activity extensively as reported earlier. Rabbit antiserum to FB did not show a precipitin band with purified Factor B, nor did the antibody inhibit Factor B stimulated activity of the AE-particles. The data suggest that FB and Factor B are two different molecular species with different functions and fail to provide evidence that FB is a coupling factor. |
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