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Chemistry of ATP synthesis
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CHAPTER 1: LIPIDS
CHAPTER 2: PROTEINS
CHAPTER 3: CARBOHYDRATES
CHAPTER 4 - NUCLEIC ACIDS
CHAPTER 5: BINDING
CHAPTER 6 - TRANSPORT AND KINETICS
CHAPTER 7 - CATALYSIS
CHAPTER 8: OXIDATIVE-PHOSPHORYLATION
CHAPTER 9 - SIGNAL TRANSDUCTION
Chapter 10: METABOLIC PATWAYS
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Korman and McLick's Pseudorotation Mechanism

Korman has studied phosphate chemistry since the 1960s, and has been well established in the literature for quite some time. His first paper (2) was published in the Proceedings of the National Academy of the Sciences in 1970, followed by a second paper (2) in 1972, as well as subsequent review articles (3-4), including an article published in Nature in 1974.(5)

Korman and McLick's Pseudorotation Mechanism describes the process of ATP synthesis by using a pentavalent phosphorous transition state. This stereochemical reaction mechanism is outlined in the following image, represented with permission from the author.(2) Section (a) shows an ADP molecule apically attacking a phosphate group held in place on the opposing apical face by a Mg-O bond to the enzyme. Section (b) shows that the geometry of the phosphorous is now pentavalent, where it then undergoes a rearrangement (c) to take on a new stereochemical conformation, so that the newly attached ADP group becomes equatorial. Sections (d) and (d') show how the unstable pentavalent transition state reverts back to a tetrahedral conformation by having one of the two protonated oxygen atoms leaves as water.

The image below, reproduced and modified with permission of the author (2), shows more clearly how the transition from the state shown above in section (b) rearranges in three dimensions to the image depicted above in section (c). The purple sphere is phosphorous, P. The red spheres are oxygen atoms who begin as equatorial and become axial. The white spheres are te remaining oxygens. Note that only one white sphere remains axial through the mechanism (i.e. the one which is on top in this image).

The following animated graphic I have produced to take advantage of the presentation power of the Internet, so that one may see a schematic of the mechanism in motion, in order to facilitate understanding of pseudorotation. The purple circle represents phosphorous, P; the red circles represent oxygen, O; and the light blue circle represents the remaining part of the ADP molecule. Hydrogen has been neglected to prevent confusion.

The Pseudorotation Mechanism not only explains the ease with which ATP can be created, but also explains rates of isotopic exchange between H218O and ATP, which happens approximately 15 times faster than the exchange between 32Pi and ATP. In addition, it explains the phenomenal rate of exchange between H218O and Pi, which occurs approximately 50 times faster than the exchange between 32Pi and ATP. What is more, the mechanism is so surprisingly simple and beautiful, like many of the tricks mother nature has developed.

The unfortunate element of this little niche of biochemistry is that politics and scientific grandstanding have hindered the chemical community from being properly presented with this explanation of ATP synthesis. However, as a biochemist, I have never seen any mechanism more completely and thoroughly explain the chemistry of the F1 particle. Therefore, I urge all biochemists who are interested in the field of phosphate chemistry to read Korman and McLick's work which I have referenced, so that tomorrow's understanding of ATP synthesis is not limited. Two articles have been scanned and archived in Adobe Acrobat PDF format. If you have the Adobe Acrobat Reader plug-in installed, which may be downloaded for free from Adobe, you are welcome to read these articles directly from this Internet site.

(1) Korman, E. F., McLick, J., "A Dynamic Stereochemical Reaction Mechanism for the ATP Synthesis Reaction of Mitochondrial Oxidative Phosphorylation." Proceedings of the National Academy of the Sciences (1970) 67, 3, pp. 1130-1136.

(2) Korman, E. F., McLick, J., "ATP Synthesis in Oxidative Phosphorylation: A Direct-Union Stereochemical Reaction Mechanism." Bioenergentics (1972) 3, 147-158.

(3) Korman, E. F., McLick, J., "Stereochemical Reaction Mechanism Formulations for Enzyme-Catalyzed Pyrophosphate Hydrolysis, ATP Hydrolysis, and ATP Synthesis." Bioorganic Chemistry (1973) 2, 179-190.

(4) Young, J. H., Korman, E. F., McLick, J., "On the Mechanism of ATP Synthesis in Oxidative Phosphorylation: a Review." Bioorganic Chemistry (1974) 3, 1-15.

(5) Young, J. H., McLick, J., Korman, E. F., "Pseudorotation mechanism of ATP hydrolysis in muscle contraction." Nature (1974) 249, 5456, 474-476.

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