CHEM 440
Biochemistry I
J. D. Cronk   Syllabus [ Previous | Next ] Pick a lecture:
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Lecture 34. Oxidative phosphorylation

Monday 6 December 2010

ATP synthase. Uncoupling of ETC and ATP synthesis.

Reading: Voet, Voet, and Pratt; Ch.18, pp.618-637.
34. Summary

Lecture 34 Summary

Uncoupling of ETC

ATP synthase

ATP synthase is the integral membrane molecular machine that uses the free energy of a transmembrane pH difference to drive the synthesis of ATP from ADP and Pi. Because the action is is reversible in some contexts - ATP can be hydrolyzed to drive generation of a pH difference - ATP synthase is also known as an ATPase. The major types of ATP synthase are the homologs in bacteria, and in mitochondria and chloroplasts of eukaryotic cells

These ATP synthases all consist of two major assemblies of polypeptides, an integral membrane component called Fo that functions as a proton channel. The other major assembly F1, is attached to Fo in the intact holoenzyme, and protrudes away from the membrane. F1 binds ADP and Pi or ATP in multiple sites.
The image of a model for the F1 assembly determined by X-ray crystallography is shown at right. The binding change mechanism describes the means by which ATP is synthesized in the F1 assembly by rotational catalysis. The rotation of a "camshaft" formed by the γ subunit within F1 is driven by its mechanical coupling to rotation of a ring of c subunits* in F0. The Berg-Oster model describes in detail how flow of protons from the low pH exterior to the high pH interior side of the membrane occurs if and only if the c ring rotates so as to turn the γ subunit within F1 in the direction of net ATP synthesis.   Image of a structural model of the F1 portion of the bovine ATP synthase
 

 
 

 

 

    
 

Learning objectives

Page updated 07-21-10

References

  1. Boyer PD. (1997) The ATP synthase-a splendid molecular machine. Ann Rev Biochem 66: 717-749.
 
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