The PX domain is a

phosphoinositide Phosphatidylinositol (or Inositol Phospholipid) consists of a family of lipids as illustrated on the right, where red is x, blue is y, and black is z, in the context of independent variation, a class of the phosphatidylglycerides. In such molecul ...

-binding

structural domain In molecular biology, a protein domain is a region of a protein's polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a compact folded three-dimensional structure. Many proteins consist of s ...

involved in targeting of proteins to cell membranes. This domain was first found in P40phox and p47phox domains of

NADPH oxidase NADPH oxidase (nicotinamide adenine dinucleotide phosphate oxidase) is a membrane-bound enzyme complex that faces the extracellular space. It can be found in the plasma membrane as well as in the membranes of phagosomes used by neutrophil white ...

(phox stands for phagocytic oxidase). It was also identified in many other proteins involved in membrane trafficking, including nexins, Phospholipase D, and

-3- kinases. The PX domain is structurally conserved in

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

s, although amino acid sequences show little similarity. PX domains interact primarily with

PtdIns(3)P Phosphatidylinositol 3-phosphate (PtdIns3''P'') is a phospholipid found in cell membranes that helps to recruit a range of proteins, many of which are involved in protein trafficking, to the membranes. It is the product of both the class II and II ...

lipids. However some of them bind to

phosphatidic acid Phosphatidic acids are anionic phospholipids important to cell signaling and direct activation of lipid-gated ion channels. Hydrolysis of phosphatidic acid gives rise to one molecule each of glycerol and phosphoric acid and two molecules of fatty ac ...

, PtdIns(3,4)P2, PtdIns(3,5)P2,

PtdIns(4,5)P2 Phosphatidylinositol 4,5-bisphosphate or PtdIns(4,5)''P''2, also known simply as PIP2 or PI(4,5)P2, is a minor phospholipid component of cell membranes. PtdIns(4,5)''P''2 is enriched at the plasma membrane where it is a substrate for a number of ...

, and

PtdIns(3,4,5)P3 Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)''P''3), abbreviated PIP3, is the product of the class I phosphoinositide 3-kinases (PI 3-kinases) phosphorylation of phosphatidylinositol (4,5)-bisphosphate (PIP2). It is a phospholipid tha ...

. The PX-domain can also interact with other domains and proteins.

Human proteins containing this domain

Sorting nexin Sorting nexins are a large group of proteins that are localized in the cytoplasm and have the potential for membrane association either through their lipid-binding PX domain (a phospholipid-binding motif) or through protein–protein inter ...

s contain this domain. Other examples include: *

HS1BP3 HCLS1 binding protein 3 also known as HS1BP3 is a protein which in humans is encoded by the ''HS1BP3'' gene. Function The protein encoded by this gene shares similarity with mouse Hs1bp3, an Hcls1-interacting protein that may be involved in lym ...

KIF16B Kinesin family member 16B, also known as KIF16B, is a protein which in humans is encoded by the ''KIF16B'' gene. See also * Kinesin References Further reading * * * * * * * * * * External links PDBe-KB
provides an overview of all ...

(SNX23) * NCF1; NCF1C; NCF4; NISCH *

PIK3C2A Phosphatidylinositol-4-phosphate 3-kinase C2 domain-containing alpha polypeptide is an enzyme that in humans is encoded by the ''PIK3C2A'' gene. The protein encoded by this gene belongs to the phosphoinositide 3-kinase (PI3K) family. PI3-kinases p ...

; PIK3C2B;

PIK3C2G Phosphatidylinositol-4-phosphate 3-kinase C2 domain-containing gamma polypeptide is an enzyme that in humans is encoded by the ''PIK3C2G'' gene. The protein encoded by this gene belongs to the phosphoinositide 3-kinase (PI3K) family. PI3-kinases ...

;

PLD1 Phospholipase D1 (PLD1) is an enzyme that in humans is encoded by the ''PLD1'' gene, though analogues are found in plants, fungi, prokaryotes, and even viruses. History The possibility of PLD1 was first mentioned in 1947 by authors Hanahan and C ...

;

PLD2 Phospholipase D2 is an enzyme that in humans is encoded by the ''PLD2'' gene. Function Phosphatidylcholine (PC)-specific phospholipases D (PLDs) catalyze the hydrolysis of PC to produce phosphatidic acid and choline. Activation of PC-specifi ...

;

PXK PX domain containing serine/threonine kinase also known as PXK is a protein which in humans is encoded by the ''PXK'' gene. Function PXK binds to the Na⁺/K⁺-ATPase beta-1 ( ATP1B1) and beta-3 ( ATP1B3) subunits and modulates both Na⁺/K� ...

RPS6KC1 Ribosomal protein S6 kinase delta-1 is an enzyme that in humans is encoded by the ''RPS6KC1'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''ge ...

SGK3 Serine/threonine-protein kinase Sgk3 is an enzyme that in humans is encoded by the ''SGK3'' gene. Function This gene is a member of the serine/threonine protein kinase family and encodes a phosphoprotein with a PX (phox homology) domain. The ...

;

SH3PXD2A SH3 and PX domain-containing protein 2A is a protein that in humans is encoded by the ''SH3PXD2A'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meanin ...

;

SNAG1 Sorting nexin-18 is a protein that in humans is encoded by the ''SNX18'' gene. This gene encodes a member of the sorting nexin family. Members of this family contain a phox (PX) domain, which is a phosphoinositide binding domain, and are involv ...

;

SNX9 Sorting nexin-9 is a protein that in humans is encoded by the ''SNX9'' gene. This gene encodes a member of the sorting nexin family. Members of this family contain a phox (PX) domain, which is a phosphoinositide binding domain, and are involved in ...

References

{{Protein domains Peripheral membrane proteins Protein domains