hydrogen-exporting ATPase, phosphorylative mechanism | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
EC no. | 3.6.3.6 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
|
Identifiers | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Symbol | E1-E2_ATPase | ||||||||||
Pfam | PF00122 | ||||||||||
InterPro | IPR000695 | ||||||||||
PROSITE | PDOC00139 | ||||||||||
TCDB | 3.A.3.3 | ||||||||||
OPM superfamily | 22 | ||||||||||
OPM protein | 4hqj | ||||||||||
|
The P-type plasma membrane H+
-ATPase is found in plants and fungi. For the gastric H+
/K+
ATPase (involved in the acidification of the stomach in mammals), see
Hydrogen potassium ATPase.
This enzyme belongs to the family of
hydrolases, specifically those acting on acid anhydrides to catalyse transmembrane movement of substances. To be specific, the protein is a part of the
P-type ATPase family. The
systematic name of this enzyme class is ATP phosphohydrolase (H+
-exporting).
H+
-exporting ATPase is also known as proton ATPase or more simply proton pump. Other names in common use include proton-translocating ATPase, yeast plasma membrane H+
-ATPase, plant plasma membrane H+
-ATPase, yeast plasma membrane ATPase, plant plasma membrane ATPase, and ATP phosphohydrolase.
The yeast ( Saccharomyces cerevisiae) enzyme is encoded by the gene Pma1 and hence referred to as Pma1p. [1]
The plasma membrane H+
-
ATPase or proton pump creates the
electrochemical gradients in the
plasma membrane of
plants,
fungi,
protists, and many
prokaryotes. Here, proton gradients are used to drive
secondary transport processes. As such, it is essential for the uptake of most
metabolites, and also for plant responses to the environment (e.g., movement of leaves).
Plasma membrane H+
-ATPases are specific for
plants,
fungi, and
protists; and
Na+
/K+
-ATPases are specific for
animal cells. These two groups of
P-type ATPases, although not from the same subfamily, seem to perform a complementary function in plants/fungi/protists and animal cells, namely the creation of an
electrochemical gradient used as an energy source for
secondary transport.
[2]
Structural information on P-type plasma membrane (PM) proton ATPases are scarce compared to that obtained for
SERCA1a. A low resolution structure from 2D crystals of the PM H+
-ATPase from
Neurospora crassa is, as of medio 2011, the only structural information on the fungal H+
-ATPase.
[3] For the plant counterpart, a crystal structure of the AHA2 PM H+
-ATPase from
Arabidopsis thaliana has been obtained from 3D crystals with a resolution of 3.6 Å.
[4] The structure of AHA2 clearly identifies three cytosolic domains corresponding to the N (nucleotide binding), P (phosphorylation), and A (actuator) domains, similar to those observed in the
SR Ca2+
-ATPase and also verifies the presence of ten transmembrane helices. The 3D crystal structure shows the AHA2 PM H+
-ATPase in a so-called quasi-occluded E1 state with the non-hydrolysable ATP analogue AMPPCP bound, and the overall fold of the catalytic unit reveals a high degree of structural similarity to the
SR Ca2+
-ATPase and the
Na+
,K+
-ATPase. The overall arrangement of the domains is similar to that observed for the occluded E1 conformation of the
SR Ca2+
-ATPase, and based on comparison with structural data for the other conformations of the
SR Ca2+
-ATPase, it was suggested that the structure of the AHA2 PM H+
-ATPase represents a novel E1 intermediate.
[4] A distinct feature of the PM H+
-ATPase not observed in other P-type ATPases is the presence of a large cavity in the transmembrane domain formed by M4, M5 and M6.
Precise regulation of PM H+
-ATPase activity is crucial to the plant. Over-expression of the PM H+
-ATPase is compensated by a down-regulation of activity,
[5] whereas deletion of an isoform is compensated by redundancy as well as augmented activity of other isoforms by increased level of post-translational modifications.
[6]
The PM H+
-ATPase is subject to autoinhibition, which negatively regulates the activity of the pump and keeps the enzyme in a low activity state where ATP hydrolytic activity is partly uncoupled from ATP hydrolysis,.
[7]
[8] Release from the autoinhibitory restraints requires posttranslational modifications such as phosphorylation and interacting proteins.
Autoinhibition is achieved by the N- and C-termini of the protein - communication between the two termini facilitates the necessary precise control of pump activity.
[9] The autoinhibitory C-terminal domain can be displaced by phosphorylation of the penultimate Thr residue and the subsequent binding of 14-3-3 proteins.
[10]
[11] The PM H+
-ATPase is the first P-type ATPase for which both termini have been demonstrated to take part in the regulation of protein activity.
[9]
Plasma membrane H+
-ATPases are found throughout the plant in all cell types investigated, but some cell types have much higher concentrations of H+
-ATPase than others. In general, these cell types are specialised for intensive
active transport and accumulate solutes from their surroundings. Most studies of these roles come from genetic studies on Arabidopsis thaliana.
[12] H+
-ATPases in plants are expressed from a multigene subfamily, and Arabidopsis thaliana for instance, have 12 different H+
-ATPase genes.
Some important physiological processes the plant H+
-ATPase is involved in are:
hydrogen-exporting ATPase, phosphorylative mechanism | |||||||||
---|---|---|---|---|---|---|---|---|---|
Identifiers | |||||||||
EC no. | 3.6.3.6 | ||||||||
Databases | |||||||||
IntEnz | IntEnz view | ||||||||
BRENDA | BRENDA entry | ||||||||
ExPASy | NiceZyme view | ||||||||
KEGG | KEGG entry | ||||||||
MetaCyc | metabolic pathway | ||||||||
PRIAM | profile | ||||||||
PDB structures | RCSB PDB PDBe PDBsum | ||||||||
Gene Ontology | AmiGO / QuickGO | ||||||||
|
Identifiers | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Symbol | E1-E2_ATPase | ||||||||||
Pfam | PF00122 | ||||||||||
InterPro | IPR000695 | ||||||||||
PROSITE | PDOC00139 | ||||||||||
TCDB | 3.A.3.3 | ||||||||||
OPM superfamily | 22 | ||||||||||
OPM protein | 4hqj | ||||||||||
|
The P-type plasma membrane H+
-ATPase is found in plants and fungi. For the gastric H+
/K+
ATPase (involved in the acidification of the stomach in mammals), see
Hydrogen potassium ATPase.
This enzyme belongs to the family of
hydrolases, specifically those acting on acid anhydrides to catalyse transmembrane movement of substances. To be specific, the protein is a part of the
P-type ATPase family. The
systematic name of this enzyme class is ATP phosphohydrolase (H+
-exporting).
H+
-exporting ATPase is also known as proton ATPase or more simply proton pump. Other names in common use include proton-translocating ATPase, yeast plasma membrane H+
-ATPase, plant plasma membrane H+
-ATPase, yeast plasma membrane ATPase, plant plasma membrane ATPase, and ATP phosphohydrolase.
The yeast ( Saccharomyces cerevisiae) enzyme is encoded by the gene Pma1 and hence referred to as Pma1p. [1]
The plasma membrane H+
-
ATPase or proton pump creates the
electrochemical gradients in the
plasma membrane of
plants,
fungi,
protists, and many
prokaryotes. Here, proton gradients are used to drive
secondary transport processes. As such, it is essential for the uptake of most
metabolites, and also for plant responses to the environment (e.g., movement of leaves).
Plasma membrane H+
-ATPases are specific for
plants,
fungi, and
protists; and
Na+
/K+
-ATPases are specific for
animal cells. These two groups of
P-type ATPases, although not from the same subfamily, seem to perform a complementary function in plants/fungi/protists and animal cells, namely the creation of an
electrochemical gradient used as an energy source for
secondary transport.
[2]
Structural information on P-type plasma membrane (PM) proton ATPases are scarce compared to that obtained for
SERCA1a. A low resolution structure from 2D crystals of the PM H+
-ATPase from
Neurospora crassa is, as of medio 2011, the only structural information on the fungal H+
-ATPase.
[3] For the plant counterpart, a crystal structure of the AHA2 PM H+
-ATPase from
Arabidopsis thaliana has been obtained from 3D crystals with a resolution of 3.6 Å.
[4] The structure of AHA2 clearly identifies three cytosolic domains corresponding to the N (nucleotide binding), P (phosphorylation), and A (actuator) domains, similar to those observed in the
SR Ca2+
-ATPase and also verifies the presence of ten transmembrane helices. The 3D crystal structure shows the AHA2 PM H+
-ATPase in a so-called quasi-occluded E1 state with the non-hydrolysable ATP analogue AMPPCP bound, and the overall fold of the catalytic unit reveals a high degree of structural similarity to the
SR Ca2+
-ATPase and the
Na+
,K+
-ATPase. The overall arrangement of the domains is similar to that observed for the occluded E1 conformation of the
SR Ca2+
-ATPase, and based on comparison with structural data for the other conformations of the
SR Ca2+
-ATPase, it was suggested that the structure of the AHA2 PM H+
-ATPase represents a novel E1 intermediate.
[4] A distinct feature of the PM H+
-ATPase not observed in other P-type ATPases is the presence of a large cavity in the transmembrane domain formed by M4, M5 and M6.
Precise regulation of PM H+
-ATPase activity is crucial to the plant. Over-expression of the PM H+
-ATPase is compensated by a down-regulation of activity,
[5] whereas deletion of an isoform is compensated by redundancy as well as augmented activity of other isoforms by increased level of post-translational modifications.
[6]
The PM H+
-ATPase is subject to autoinhibition, which negatively regulates the activity of the pump and keeps the enzyme in a low activity state where ATP hydrolytic activity is partly uncoupled from ATP hydrolysis,.
[7]
[8] Release from the autoinhibitory restraints requires posttranslational modifications such as phosphorylation and interacting proteins.
Autoinhibition is achieved by the N- and C-termini of the protein - communication between the two termini facilitates the necessary precise control of pump activity.
[9] The autoinhibitory C-terminal domain can be displaced by phosphorylation of the penultimate Thr residue and the subsequent binding of 14-3-3 proteins.
[10]
[11] The PM H+
-ATPase is the first P-type ATPase for which both termini have been demonstrated to take part in the regulation of protein activity.
[9]
Plasma membrane H+
-ATPases are found throughout the plant in all cell types investigated, but some cell types have much higher concentrations of H+
-ATPase than others. In general, these cell types are specialised for intensive
active transport and accumulate solutes from their surroundings. Most studies of these roles come from genetic studies on Arabidopsis thaliana.
[12] H+
-ATPases in plants are expressed from a multigene subfamily, and Arabidopsis thaliana for instance, have 12 different H+
-ATPase genes.
Some important physiological processes the plant H+
-ATPase is involved in are: