Plasma membrane calcium transporting ATPase isoform 2

The alpha chains of sodium/potassium-transporting ATPases (H⁺/K⁺ and Na⁺/K⁺-ATPase) catalyze the hydrolysis of ATP, coupled with the exchange of sodium and potassium ions across the plasma membrane. The proteins are located in the cell membrane , the ion transport they mediate creating the electro-chemical gradient that provides the energy for the active transport of various nutrients. H⁺/K⁺-transporting ATPases are also responsible for production of acid in the stomach . H⁺/K⁺ and Na⁺/K⁺-ATPase are members of the P-type (or E1-E2-type) cation-transporting ATPase superfamily, which has evolved from a common ancestral gene . The sequences contain 10 transmembrane (TM) helices, some of which are well conserved throughout the superfamily. They may thus all operate via a similar mechanism, with an aspartylphosphoryl enzyme intermediate being formed during the catalytic cycle.

The alpha chains of sodium/potassium-transporting ATPases (H⁺/K⁺ and Na⁺/K⁺-ATPase) catalyze the hydrolysis of ATP, coupled with the exchange of sodium and potassium ions across the plasma membrane. The proteins are located in the cell membrane , the ion transport they mediate creating the electro-chemical gradient that provides the energy for the active transport of various nutrients. H⁺/K⁺-transporting ATPases are also responsible for production of acid in the stomach . H⁺/K⁺ and Na⁺/K⁺-ATPase are members of the P-type (or E1-E2-type) cation-transporting ATPase superfamily, which has evolved from a common ancestral gene . The sequences contain 10 transmembrane (TM) helices, some of which are well conserved throughout the superfamily. They may thus all operate via a similar mechanism, with an aspartylphosphoryl enzyme intermediate being formed during the catalytic cycle. Members of these families are involved in Na+/K⁺, H+/K⁺, Ca²⁺ and Mg²⁺- transport.

P-type (or E1-E2-type) ATPases constitute a superfamily of cation transport enzymes, present both in prokaryota and eukaryota, whose members mediate membrane flux of all common biologically relevant cations . The enzymes, that form an aspartyl phosphate intermediate in the course of ATP hydrolysis, can be divided into 4 major groups : (1) Ca²⁺-transporting ATPases; (2) Na⁺/K⁺- and gastric H⁺/K⁺-transporting ATPases; (3) plasma membrane H⁺-transporting ATPases (proton pumps) of plants, fungi and lower eukaryotes; and (4) all bacterial P-type ATPases, except the Mg²⁺-ATPase of Salmonella typhimurium, which is more similar to the eukaryotic sequences. However, great variety of sequence analysis methods results in diversity of classification.

P-type (or E1-E2-type) ATPases constitute a superfamily of cation transport enzymes, present both in prokaryota and eukaryota, whose members mediate membrane flux of all common biologically relevant cations . The enzymes, that form an aspartyl phosphate intermediate in the course of ATP hydrolysis, can be divided into 4 major groups : (1) Ca²⁺-transporting ATPases; (2) Na⁺/K⁺- and gastric H⁺/K⁺-transporting ATPases; (3) plasma membrane H⁺-transporting ATPases (proton pumps) of plants, fungi and lower eukaryotes; and (4) all bacterial P-type ATPases, except the Mg²⁺-ATPase of Salmonella typhimurium, which is more similar to the eukaryotic sequences. However, great variety of sequence analysis methods results in diversity of classification. According to PRINTS signatures, P-type ATPase superfamily is divided into six groups (each of them has its own IPR number). And the entries of these groups can match the previous classification in the following way: IPR006069 fits group 2; IPR000695 fits group 3; IPR001366, IPR001756 and IPR001877 fit group 4. Graduation into four major groups is more biologically relevant, as it correlates with cation specificities and biological sources of P-type ATPase.

Members of this families are involved in Na+/K+, H+/K+, Ca++ and Mg++ transport.

This group of hydrolase enzymes is structurally different from the alpha/beta hydrolase family (abhydrolase). This group includes L-2-haloacid dehalogenase, epoxide hydrolases and phosphatases. The structure consists of two domains. One is an inserted four helix bundle, which is the least well conserved region of the alignment, between residues 16 and 96 of HAD1_PSESP. The rest of the fold is composed of the core alpha/beta domain.

This family describes the P-type ATPase responsible for translocating calcium ions across the plasma membrane of eukaryotes , out of the cell. In some organisms, this type of pump may also be found in vacuolar membranes . In humans and mice, at least, there are multiple isoforms of the PMCA pump with overlapping but not redundant functions. Accordingly, there are no human diseases linked to PMCA defects, although alterations of PMCA function do elicit physiological effects . The calcium P-type ATPases have been characterized as Type IIB based on a phylogenetic analysis which distinguishes this group from the Type IIA SERCA calcium pump .