Structural Studies
Structural information on P-type proton ATPases are scarce compared to that obtained for SERCA1a. A low resolution structure from 2D crystals of the plasma membrane (PM) H+
-ATPase from Neurospora crassa is, as of medio 2011, the only structural information on the fungal H+
-ATPase. 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. 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. 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.
Read more about this topic: Proton ATPase
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