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The 'pleckstrin homology' (PH) domain is a domain of about 100 residues that occurs in a wide range of proteins involved in intracellular signaling or as constituents of the cytoskeleton [1,2,3,4,5,6,7].

The function of this domain is not clear, several putative functions have been suggested:

• binding to the β/γ subunit of heterotrimeric G proteins,
• binding to lipids, e.g. phosphatidylinositol-4,5-bisphosphate,
• binding to phosphorylated Ser/Thr residues,
• attachment to membranes by an unknown mechanism.

It is possible that different PH domains have totally different ligand requirements.

The 3D structure of several PH domains has been determined [8]. All known cases have a common structure consisting of two perpendicular anti-parallel β sheets, followed by a C-terminal amphipathic helix. The loops connecting the β-strands differ greatly in length, making the PH domain relatively difficult to detect. There are no totally invariant residues within the PH domain.

Proteins reported to contain one more PH domains belong to the following families:

• Pleckstrin, the protein where this domain was first detected, is the major substrate of protein kinase C in platelets. Pleckstrin is one of the rare proteins to contains two PH domains.
• Ser/Thr protein kinases such as the Act/Rac family, the β-adrenergic receptor kinases, the mu isoform of PKC and the trypanosomal NrkA family.
• Tyrosine protein kinases belonging to the Btk/Itk/Tec subfamily.
• Insulin Receptor Substrate 1 (IRS-1).
• Regulators of small G-proteins like guanine nucleotide releasing factor GNRP (Ras-GRF) (which contains 2 PH domains), guanine nucleotide exchange proteins like vav, dbl, SoS and yeast CDC24, GTPase activating proteins like rasGAP and BEM2/IPL2, and the human break point cluster protein bcr.
• Cytoskeletal proteins such as dynamin (see <PDOC00362>), Caenorhabditis elegans kinesin-like protein unc-104 (see <PDOC00343>), spectrin β- chain, syntrophin (2 PH domains) and yeast nuclear migration protein NUM1.
• Mammalian phosphatidylinositol-specific phospholipase C (PI-PLC) (see <PDOC50007>) isoforms γ and delta. Isoform γ contains two PH domains, the second one is split into two parts separated by about 400 residues.
• Oxysterol binding proteins (OSBPs).
• Mouse protein citron, a putative rho/rac effector that binds to the GTP- bound forms of rho and rac,
• Several yeast proteins involved in cell cycle regulation and bud formation like BEM2, BEM3, BUD4 and the BEM1-binding proteins BOI2 (BEB1) and BOI1 (BOB1).
• Caenorhabditis elegans protein mig-10.
• Caenorhabditis elegans hypothetical proteins C04D8.1, K06H7.4 and ZK632.12.
• Yeast hypothetical proteins YBR129c and YHR155w.

The profile for the PH domain, which has been developed by Toby Gibson at the EMBL, covers the total length of domain. Several proteins contain large insertions in the PH domain and are thus difficult to detect with this profile. In some of these cases, the profile will align only to one half of the PH domain.

Gibson T.J.

March 2002 / Text revised.

PROSITE method (with tools and information) covered by this documentation:

PH_DOMAIN, PS50003; PH domain profile  (MATRIX)

Sequences known to belong to this class detected by the pattern: ALL. But it should be noted that while all sequences containing PH domains are detected, not all PH domains are. Some of the split domains lie below the cutoff threshold Other sequence(s) detected in Swiss-Prot: NONE.

• Domain architecture view of Swiss-Prot proteins matching PS50003 • Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS50003 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS50003 • Scan Swiss-Prot/TrEMBL entries against PS50003 • view ligand binding statistics

Matching PDB structures: 1AWE 1B55 1BAK 1BTK ... [ALL]

1	Authors	Mayer B.J., Ren R., Clark K.L., Baltimore D.
	Title	A putative modular domain present in diverse signaling proteins.
	Source	Cell 73:629-630(1993).
	PubMed ID	8500161

2	Authors	Haslam R.J., Koide H.B., Hemmings B.A.
	Title	Pleckstrin domain homology.
	Source	Nature 363:309-310(1993).
	PubMed ID	8497315
	DOI	10.1038/363309b0

3	Authors	Musacchio A., Gibson T.J., Rice P., Thompson J., Saraste M.
	Title	The PH domain: a common piece in the structural patchwork of signalling proteins.
	Source	Trends Biochem. Sci. 18:343-348(1993).
	PubMed ID	8236453

4	Authors	Gibson T.J., Hyvonen M., Musacchio A., Saraste M., Birney E.
	Title	PH domain: the first anniversary.
	Source	Trends Biochem. Sci. 19:349-353(1994).
	PubMed ID	7985225

5	Authors	Pawson T.
	Title	Protein modules and signalling networks.
	Source	Nature 373:573-580(1995).
	PubMed ID	7531822
	DOI	10.1038/373573a0

6	Authors	Ingley E., Hemmings B.A.
	Title	Pleckstrin homology (PH) domains in signal transduction.
	Source	J. Cell. Biochem. 56:436-443(1994).
	PubMed ID	7890802

7	Authors	Saraste M., Hyvonen M.
	Title	Pleckstrin homology domains: a fact file.
	Source	Curr. Opin. Struct. Biol. 5:403-408(1995).
	PubMed ID	7583640

8	Authors	Riddihough G.
	Title	More meanders and sandwiches.
	Source	Nat. Struct. Biol. 1:755-757(1994).
	PubMed ID	7634082

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