Conformational basis of energy transduction in mitochondria
The conformational mechanism of energy transduction which we proposed in 1967 was based on an intuitive evaluation of the significance of large amplitude configurational changes which parallel energized processes in mitochondria [l-3] . By now a considerable body of information has been accumulated about the details of the configurational transitions in the mitochondrion [4-61. Moreover, the theory of structured systems with the capability for conservation of energy by a conformational mechanism is now being developed systematically [7]. This interplay of experiment and theory has made it possible to formulate the conformational hypothesis more explicitly and precisely. The tripartite repeating unit of the cristal membrane is the molecular unit of mitochondrial energy transduction. While in theory each repeating unit is a complete operational unit, in practice we are dealing with two dimensional arrays of repeating units within a membrane continuum and with the cooperative effects intrinsic to such arrays. Each repeating unit contains three basic systems which collectively effectuate the conformational transduction of energy. These systems are (a) the primary energizing system (one of the complexes of the electron transfer chain), (b) the conformational frame system, and (c) the discharge-directing system (the ATPase complex is one such system). The electron transfer process within each complex of the chain leads to a conformational transition [8-lo]. But since the electron transfer system is enclosed within a rigid frame (the conformational frame system [ 7]), the conformational expansion of
Ultrastructure of Diplodia maydis grown on selected synthetic media
AbstractOf all the fixatives studied, glutaraldehyde followed by osmium was considered best. Fixation temperatures did not result in ultrastructural differences. Holdover for short periods (up to 7 days) in 70% alcohol and long periods (3 months) in glutaraldehyde did not result in ultrastructural differences from those processed without a hold-over period. Uranyl acetate increased contrast, as expected. Epon was selected over Epon-Araldite (more viscous) and Spurr's resin (less contrast). Generally, growth conditions did not alter gross hyphal morphology, although cytological changes were noted.
Diplodia maydis is morphologically similar to ascomycetous fungi. It contained typical organelles as found in other fungi, e.g. cell wall, septa, Woronin bodies, nuclei, mitochondria, endoplasmic reticulum, lomasomes, plasma membranes, cytosomes, vacuoles, storage materials (lipids, carbohydrates and intracellular and extracellular electrondense substances), thickened mycelial strands, and intrahyphal hyphae. Bead-like structures and thickened nodes as observed by SEM were accounted for by structures observed by TEM. Mitochondria were dramatically elongated, and in one case, branched. Hyphae were organized in three zones: apical, subapical, and vacuolated. Apical vesicles were thought to account for cell extension. Evidence was presented that Woronin bodies originated from microbodies. It was suggested that the Golgi apparatus consists of isolated single cisternae. Free ribo- or polysomes (without ER) were suggested as the site of the majority of protein synthesis. Continuities and configurations of plasma and outer nuclear and mitochondrial membranes, ER, cytosomes, vacuoles and storage materials suggested that a system similar to Morre et al's endomembrane system is in operation in D. maydis to account for component flow and differentiation.
Glutaraldehyde-fixed mitochondria. I. Enzyme activity, ion translocation, and conformational changes.
Abstract A sucrose density gradient technique for the rapid and controlled fixation of mitochondria by glutaraldehyde has been developed. Glutaraldehyde-fixed mitochondria retain the capacity to oxidize substrates. Fixation is made to a degree where the nonionic detergent, Triton X-100, is incapable of changing conformation. Fixation inhibits various energy-dependent processes as respiratory stimulation by dinitrophenol, calcium, or ADP; the capacity for ATP synthesis and hydrolysis; and energy-linked conformational changes associated with ion transport. The data are consistent with, but do not prove, that conformational changes per se are required for energy transfer, for no condition has been found in which this is untrue. Fixed mitochondria retain the capacity to develop proton gradients with calcium. Triton X-100 does not affect conformation but does apparently interact with lipid to dispel gradients established to charged ions. Mitochondria have been fixed in contracted and swollen conformation. Swollen fixed mitochondria lose the capacity to maintain proton gradients. It is concluded that glutaraldehyde fixation provides a sensitive means for preserving electron transfer and for retaining the capacity for mitochondria to develop ion gradients in the absence of osmotic volume changes.