Skip to content
Login Register

#ATP synthesis

16 public questions tagged with this topic.

Membrane Transportation

F-type ATPases differ from other ATPases because they:

F-type ATPases, historically termed FoF1 ATP synthases, represent an evolutionary unique class of rotary translocases that normally synthesize rather than consume ATP. While P-type and V-type pumps hydrolyze ATP to build H+ or Ca2+ gradients, F-type complexes harness pre-existing proton motive force created by electron transport chains in mitochondria, chloroplast thylakoids, and bacterial plasma membranes. The membrane-embedded Fo sector contains an oligomeric c-ring that binds protons via conserved carboxylate, rotating against subunit a as protons move down gradient. This rotation drives the central gamma-epsilon stalk inside the alpha3beta3 F1 hexamer, forcing beta subunits through open, loose and tight conformations that bind ADP and inorganic phosphate and condense them into ATP via binding-change mechanism. Isolated enzymes reversibly hydrolyze ATP to pump protons when proton motive force collapses, but physiological role is ATP production, supplying bulk of cellular ATP for biosynthesis, motility and transport work. Such chemiosmotic coupling explains oxidative phosphorylation and photophosphorylation efficiency.

Ref: Stock et al., Curr Opin Struct Biol 2000, ATP synthase rotary mechanism; Alberts, Chapter 14.

View Details
Membrane Transportation

F-class ATPases are primarily involved in:

F-type ATPases, often called ATP synthases, are evolutionarily related to V-type pumps but adapted for opposite physiological purpose in most contexts. Located in bacterial plasma membrane, mitochondrial inner membrane cristae and chloroplast thylakoid membrane, they consist of soluble F1 catalytic head containing alternating alpha and beta subunits around central gamma stalk and membrane embedded Fo base containing a subunit and c-ring proton channel. In respiring membranes electron transport complexes pump protons outward creating proton motive force combination of pH gradient and electrical potential about 200 millivolts. Protons re-enter through Fo c-ring causing rotation of c-ring and gamma which cyclically distorts beta subunits alternating among open, loose and tight states per Boyer's binding change mechanism, converting ADP plus inorganic phosphate into ATP. This mode uses reverse proton transport relative to typical pump direction, transforming electrochemical energy into chemical energy. ATP hydrolysis driven proton pumping occurs when gradient collapses, but principal cellular role remains synthesis not simply hydrolysis for ion transport.

Ref: Boyer, Nobel Lecture 1997, F-Type ATP Synthase Rotary Mechanism and ATP Synthesis.

View Details