P-type ATPase - Phylogenetic Classification

Phylogenetic Classification

A phylogenetic analysis of 159 sequences made in 1998 by Axelsen and Palmgren showed that P-type ATPases can be divided into five subfamilies, based strictly on a conserved sequence kernel excluding the highly variable N and C terminal regions. The phylogenetic analysis grouped the proteins independent of the organism from which they are isolated and showed that the diversification of the P-type ATPase family occurred prior to the separation of eubacteria, archaea, and eucaryota. This underlines the significance of this protein family for cell survival.

• Type I consists of the transition/heavy metal ATPases.
  • Type IA ATPases are involved in K+ import. They are atypical P-type ATPases because, unlike other P-type ATPases, they function as part of a heterotetrameric complex (called KdpFABC), where the actual K+ transport is mediated by another subcomponent of the complex.
  • Type IB ATPases are involved in transport of the soft Lewis acids: Cu+, Ag+, Cu2+, Zn2+, Cd2+, Pb2+ and Co2+. They are key elements for metal resistance and metal homeostasis in a wide range of organisms.

• Type II ATPases are split into four groups.
  • Type IIA transports Ca2+. SERCA1a is a type IIA pump.
  • Type IIB transports Ca2+.
  • Type IIC consists of the closely related Na+/K+ and H+/K+ ATPases from animal cells.
  • Type IID contains a small number of fungal ATPases of unknown function.

• Type III ATPases contains the plasma membrane H+-ATPases from plants and fungi (IIIA) and a small subdivision with Mg2+-ATPases from three bacterial species (IIIB).

• Type IV ATPases have been shown to be involved in the transport of phospholipids., such as phosphatidylserine, phosphatidylcholine and phosphatidylethanolamine.

• Type V ATPases have unknown specificity. This large group are only found in eukaryotes and are believed to be involved in cation transport in the endoplasmic reticulum.