Ephraim F. Korman

Studies on the transition of the cristal membrane from the orthodox to the aggregated configuration. I: Topology of bovine adrenal cortex mitochondria in the orthodox configuration

Bovine adrenal cortex mitochondria examined by electron microscopyin situ orin vitro in 0·25 M sucrose have an unusual cristal membrane structure. The cristae usually appear as unconnected vesicles within a double membrane system. A few of the vesicles appear to be attached to the inner boundary membrane or to one or more other vesicles. The configuration of such mitochondria will be defined as the orthodox configuration. In this communication we will provide evidence that the inner membrane is not composed of multiple vesicles, but is one continuous membrane with tubular invaginations, and that these invaginations alternately are ballooned out and squeezed down. A mechanism has been proposed to account for the differentiated structure of the cristae of adrenal cortex mitochondria.

On the mechanism of ATP synthesis in oxidative phosphorylation: A review

Abstract It is shown that the presently available evidence supports the existence of two entry points for water oxygen in the mitochondrial oxygen exchanges. This in turn provides support for the pseudorotation reaction mechanism of ATP synthesis which is the only mechanism of ATP synthesis proposed to date allowing for two entry points of water oxygen. It is also shown that the pseudorotation mechanism can resolve the apparent paradox of a P 1 ⇆ H 2 O exchange·separate from the reversal of phosphorylation yet dependent on the mechanism of P 1 activation. In addition an interpretation consistent with the experimental observations concerning As i -induced stimulation of respiration and effects associated with oligomycin and aurovertin is shown to follow from the analysis of the oxygen exchanges. Implications of the pseudorotation mechanism for the mechanism of energy coupling in oxidative phosphorylation are discussed.

Stereochemical reaction mechanism formulations for enzyme-catalyzed pyrophosphate hydrolysis, ATP hydrolysis, and ATP synthesis

Abstract Fundamental concepts pertaining to the stereochemistry paths of polar additionelimination (nucleophilic substitution) reactions at phosphate phosphorus centers are reviewed and employed to analyze 18O exchange reactions catalyzed by inorganic pyrophosphatase and mitochondrial ATP synthetase. The analysis suggests reasonable choices for the stereochemistry path of the 18O exchanges. This, in turn, permits reasonable choices for the stereochemistry paths of hydrolysis of pyrophosphate catalyzed by pyrophosphatase and of hydrolysis and synthesis of ATP catalyzed by ATP synthetase.

On the structure of biological membranes: the double-tiered pattern.

A set of six biological membranes has been examined electron microscopically in positively-stained sections at both low and high resolution. At low resolution, all six membranes exhibit a “railroad track” pattern, while at high resolution all six membranes exhibit a pattern of a double-tier of globular “particles”. The correspondence between the railroad track pattern and the double-tiered pattern is considered. The relationship of the double-tiered pattern to the bimodal properties of the constituent protein and phospholipid molecules is discussed.

The discovery of fructose-1,6-diphosphate (the harden-young ester) in the molecularization of fermentation and of bioenergetics

SummaryEarly in the twentieth centuryHarden andYoung extended the work ofBuchner on cell-free alcoholic fermentation by the observation that salts of orthophosphoric acid stimulate that fermentation.Wroblewski had made a similar observation beforeHarden andYoung. By concerning themselves with the intermediate fate of phosphate rather than with the “buffering” capacity of phosphate as hadWroblewski to explain the stimulation,Harden andYoung were led to the discovery of a sugar diphosphate in the system. That compound, which became known as theHarden-Young ester and which later was shown to be fructose-1,6-diphosphate, was the first chemical intermediate discovered in fermentation. Its discovery let to the ultimate description of fermentation in terms of molecular intermediates, i.e., to the “molecularization” of fermentation.

ATP Synthesis in Oxidative Phosphorylation: A Direct-Union Stereochemical Reaction Mechanism

A fundamental understanding of oxidative phosphorylation will involve chemical reaction mechanisms. Since chemical reaction mechanisms describe in detail the making and/or breaking of chemical bonds, before a meaningful reaction mechanism can be formulated for a given reaction, the actual bonds involved must be known. This applies to all chemical reactions, including the chemical reactions in oxidative phosphorylation.

ATP Synthesis in Mitochondrial Oxidative Phosphorylation

I would like to tell you about some recent work done at the Enzyme Institute on a chemical reaction mechanism for the ATP synthesis part of mitochondrial oxidative-phosphorylation. This work was carried out by Dr. Jerome McLick and myself, and is called the KORMAN-McLICK mechanism for mitochondrial ATP synthesis(1).