Alice Clark/ATPsynthase

ATP synthase is shown here to the right in 3D with each protein shown in a different colour.

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Exploring the ATP synthase molecule

ATP synthase is a cellular molecular motor found in the mitochondrial membrane of humans, and also in other organisms. It has a role in the generation of ATP, the cells energy currency. This large molecule is built up of a number of different groups of proteins: the F0, the F1, and the stator - each group has an important role to play.

The contains alpha (shown in light blue) and beta (shown in dark blue), and making up the axel, the protein chain.

Q1: Describe how the protein chains are arranged to comprise the F1 region?

The F1 can have adenosine diphosphate (ADP) molecules and adenosine triphosphate (ATP) in the nucleotide binding sites. See if you can zoom in on the ATP identify the phosphate atoms (orange). ==>

The three sites primarily located in the β subunits carry active ATP synthesis. The sites primarily located in the α subunits are non-catalytic and exchange bound nucleotide very slowly, they are thought to be a carry over from evolution, and now play a more regulatory role.

Q2: How many phosphates atoms (orange) does ATP have, and how does this differ to ADP?

Q3: Which atoms is the high energy bond formed between, within ATP (the bond that the ATP synthase catalyses within the β subunits)?

The rotates at 120 degree steps, putting the motor into three different conformations, as the ADP and phosphate binds, the high energy bond is formed and the ATP is released.

Q4: What is the role of the axel, explain how it effects the β subunits?

is a circular rotor that is formed of alpha helices that sit in the mitochondrial membrane. The hydrogen ions travel around the circular F0 motor, and turning the rotor in the process, much like a water wheel. The hydrogen's are passed alone a chain of (amino acids) in the F0 motor, and then transferred to an (Arg) amino acid. The arginine passes the hydrogen to the rotor, which turns all the way around. Then the hydrogen is then passed to the opposite side of the membrane.

Q5: What is the location and role of the FO region?

Q6: Name two key amino acids, one acidic and one basic, that bind the hydrogen's within the the F0, during the ATP generation process?

Summary

The synthesis of ATP, the cells energy currency, involves a number of steps performed by a tiny molecular motor, found in the mitochondrial membrane, called ATP synthase.

1. Binding of ADP and phosphate to the ATP synthase beta domain located in the F1 domain

2. Formation of the new high energy phosphate-phosphate bond between the ADP and phosphate using energy, generated by the hydrogens moving the F0, then the movement is transmitted by the axel to the F1 region.

3. Releasing the newly made ATP from the F1 region

Key Terms

Aspartic acid = an acidic amino acid

Glutamic acid = an acidic amino acid

ATP = adenosine triphosphate (nucleotide)

ADP = adenosine diphosphate (nucleotide)

ATP synthase - A molecular motor that generates ATP

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