The PX domain is a
phosphoinositide-binding
structural domain
In molecular biology, a protein domain is a region of a protein's Peptide, polypeptide chain that is self-stabilizing and that Protein folding, folds independently from the rest. Each domain forms a compact folded Protein tertiary structure, thre ...
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
Phospholipase D (PLD) (EC 3.1.4.4; also known as lipophosphodiesterase II, lecithinase D, choline phosphatase; systematic name: phosphatidylcholine phosphatidohydrolase) is an anesthetic-sensitive and mechanosensitive enzyme of the phospholipa ...
, and
phosphoinositide-3-
kinase
In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule don ...
s.
The PX domain is structurally conserved in
eukaryote
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
s, although amino acid sequences show little similarity.
PX domains interact primarily with
PtdIns(3)P lipids.
However some of them bind to
phosphatidic acid,
PtdIns(3,4)P2,
PtdIns(3,5)P2
Phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) is one of the seven phosphoinositides found in eukaryotic cell membranes.
In quiescent cells, the PtdIns(3,5)P2 levels, typically quantified by HPLC, are the lowest amongst the constitutively ...
,
PtdIns(4,5)P2, and
PtdIns(3,4,5)P3. 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 Structural motif, motif) or through protein� ...
s contain this domain. Other examples include:
*
HS1BP3
*
KIF16B
Kinesin family member 16B, also known as KIF16B, is a protein which in humans is encoded by the ''KIF16B'' gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of ...
(SNX23)
*
NCF1;
NCF1C;
NCF4;
NISCH
*
PIK3C2A;
PIK3C2B;
PIK3C2G;
PLD1;
PLD2
Phospholipase D2 is an enzyme that in humans is encoded by the ''PLD2'' gene.
Function
Phosphatidylcholine (PC)-specific phospholipase D, phospholipases D (PLDs) catalyze the hydrolysis of PC to produce phosphatidic acid and choline. Activati ...
;
PXK
*
RPS6KC1
*
SGK3;
SH3PXD2A;
SNAG1;
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 i ...
References
{{Protein domains
Peripheral membrane proteins
Protein domains