ATP synthase subunit C

{{Pfam_box

| Symbol = ATP-synt_C

| Name =

| image =2bl2.png

| width =250

| caption =V-type sodium ATPase from Enterococcus hirae. Calculated hydrocarbon boundaries of the lipid bilayer are shown by red and blue dots

| Pfam= PF00137

| InterPro= IPR002379

| SMART=

| Prosite = PDOC00526

| SCOP = 1aty

| TCDB =

| OPM family= 5

| OPM protein= 2bl2

| PDB=

}}

ATPase, subunit C of Fo/Vo complex is the main transmembrane subunit of V-type, A-type and F-type ATP synthases.  Subunit C (also called subunit 9, or proteolipid in F-ATPases, or the 16 kDa proteolipid in V-ATPases) was found in the Fo or Vo complex of F- and V-ATPases, respectively. The subunits form an oligomeric c ring that make up the Fo/Vo/Ao rotor, where the actual number of subunits vary greatly among specific enzymes.{{cite journal | vauthors = Kühlbrandt W, Davies KM | title = Rotary ATPases: A New Twist to an Ancient Machine | journal = Trends in Biochemical Sciences | volume = 41 | issue = 1 | pages = 106–116 | date = January 2016 | pmid = 26671611 | doi = 10.1016/j.tibs.2015.10.006 }}

ATPases (or ATP synthases) are membrane-bound enzyme complexes/ion transporters that combine ATP synthesis and/or hydrolysis with the transport of protons across a membrane. ATPases can harness the energy from a proton gradient, using the flux of ions across the membrane via the ATPase proton channel to drive the synthesis of ATP. Some ATPases work in reverse,

using the energy from the hydrolysis of ATP to create a proton gradient. There are different types of ATPases, which can

differ in function (ATP synthesis and/or hydrolysis), structure (F-, V- and A-ATPases contain rotary motors) and in the type of ions they transport.{{cite journal |vauthors=Muller V, Cross RL |title=The evolution of A-, F-, and V-type ATP synthases and ATPases: reversals in function and changes in the H+/ATP coupling ratio |journal=FEBS Lett. |volume=576 |issue=1 |pages=1–4 |year=2004 |pmid=15473999 |doi=10.1016/j.febslet.2004.08.065|s2cid=25800744 |doi-access=free |bibcode=2004FEBSL.576....1C }}{{cite journal |vauthors=Zhang X, Niwa H, Rappas M |title=Mechanisms of ATPases--a multi-disciplinary approach |journal=Curr Protein Pept Sci |volume=5

|issue=2 |pages=89–105 |year=2004 |pmid=15078220 |doi=10.2174/1389203043486874}}

The F-ATPases (or F1Fo ATPases) and V-ATPases (or V1Vo ATPases) are each composed of two linked complexes: the F1 or V1 complex contains the catalytic core that synthesizes/hydrolyses ATP, and the Fo or Vo complex that forms the membrane-spanning pore. The F- and V-ATPases all contain rotary motors, one that drives proton translocation across the membrane and one that drives ATP synthesis/hydrolysis.{{cite journal |vauthors=Itoh H, Yoshida M, Yasuda R, Noji H, Kinosita K |title=Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase |journal=Nature |volume=410 |issue=6831 |pages=898–904 |year=2001 |pmid=11309608 |doi=10.1038/35073513|bibcode=2001Natur.410..898Y |s2cid=3274681 }}{{cite journal |vauthors=Wilkens S, Zheng Y, Zhang Z |title=A structural model of the vacuolar ATPase from transmission electron microscopy |journal=Micron |volume=36 |issue=2 |pages=109–126 |year=2005 |pmid=15629643 |doi=10.1016/j.micron.2004.10.002}}

In F-ATPases, the flux of protons through the ATPase channel drives the rotation of the C subunit ring, which in turn is coupled to the rotation of the F1 complex gamma subunit rotor due to the permanent binding between the gamma and epsilon subunits of F1 and the C subunit ring of Fo. The sequential protonation and deprotonation of Asp61 of subunit C is coupled to the stepwise movement of the rotor.{{cite journal |vauthors=Fillingame RH, Angevine CM, Dmitriev OY |title=Mechanics of coupling proton movements to c-ring rotation in ATP synthase |journal=FEBS Lett.

|volume=555 |issue=1 |pages=29–34 |year=2003 |pmid=14630314 |doi=10.1016/S0014-5793(03)01101-3|s2cid=38896804 |doi-access=free |bibcode=2003FEBSL.555...29F }}

In V-ATPases, there are three proteolipid subunits (c, c′ and c′′) that form part of the proton-conducting pore, each containing a buried glutamic acid residue that is essential for proton transport.{{cite journal |vauthors=Inoue T, Forgac M |title=Cysteine-mediated cross-linking indicates that subunit C of the V-ATPase is in close proximity to subunits E and G of the V1 domain and subunit a of the V0 domain |journal=J. Biol. Chem. |volume=280 |issue=30 |pages=27896–27903 |year=2005 |pmid=15951435 |doi=10.1074/jbc.M504890200|doi-access=free }}{{cite journal |vauthors=Jones R, Findlay JB, Harrison M, Durose L, Song CF, Barratt E, Trinick J |title=Structure and function of the vacuolar H+-ATPase: moving from low-resolution models to high-resolution structures |journal=J. Bioenerg. Biomembr. |volume=35 |issue=4 |pages=337–345 |year=2003 |pmid=14635779 |doi=10.1023/A:1025728915565|s2cid=43788207 }}

In a recent study c-subunit has been indicated as a critical component of the mitochondrial permeability transition pore.{{cite journal|last=Bonora|first=M |author2=Bononi, A |author3=De Marchi, E |author4=Giorgi, C |author5=Lebiedzinska, M |author6=Marchi, S |author7=Patergnani, S |author8=Rimessi, A |author9=Suski, JM |author10=Wojtala, A |author11=Wieckowski, MR |author12=Kroemer, G |author13=Galluzzi, L |author14=Pinton, P|title=Role of the c subunit of the FO ATP synthase in mitochondrial permeability transition.|journal=Cell Cycle|date=Feb 15, 2013|volume=12|issue=4|pages=674–83|pmid=23343770|doi=10.4161/cc.23599|pmc=3594268}}