| Description: |
P-ATPases (also known as E1-E2 ATPases) ([intenz:3.6.3.-]) are found in bacteria and in a number of eukaryotic plasma membranes and organelles []. P-ATPases function to transport a variety of different compounds, including ions and phospholipids, across a membrane using ATP hydrolysis for energy. There are many different classes of P-ATPases, which transport specific types of ion: H+, Na+, K+, Mg2+, Ca2+, Ag+and Ag2+, Zn2+, Co2+, Pb2+, Ni2+, Cd2+, Cu+and Cu2+. P-ATPases can be composed of one or two polypeptides, and can usually assume two main conformations called E1 and E2.This entry represents the copper and cadmium-type heavy metal transporting P-type ATPases, and other related sequences that belong to the IB subfamily of P-type ATPases. Type IB ATPases are involved in transport of the soft Lewis acids: Cu+, Ag+, Cu2+, Zn2+, Cd2+, Pb2+and Co2+. These proteins are involved in a variety of processes in both prokaryotes and eukaryotes. In Arabidopsis, the copper-ATPase RAN1 delivers copper to create functional hormone receptors involved in ethylene signalling []. In humans, ATP7A supplies copper to copper-dependent enzymes in the secretory pathway, while ATP7B exports copper out of the cells. Defects in ATP7B are the cause of Wilson disease (WD), an autosomal recessive disorder in which copper cannot be incorporated into ceruloplasmin in liver and cannot be excreted from the liver into the bile []. Defects in ATP7A are the cause of Menkes disease (MNKD), also known as kinky hair disease. MNKD is an X-linked recessive disorder of copper metabolism characterised by generalised copper deficiency []. |
