The BEACH domain (see <PDOC50197>) defines a large family of eukaryotic proteins that have diverse cellular functions in vesicle trafficking, membrane dynamics, and receptor signaling. The sequence homology among these proteins is limited to their C-terminal region, where they contain the PH-BEACH-WD40 domains. The WD40 domain (see <PDOC00574>) is generally located at the extreme C terminus of these proteins and may be important for protein-protein interactions. The BEACH domain is located just prior to the WD40 domain in these proteins and is the only domain that is highly conserved among them. The pleckstrin homology (PH) domain ( see <PDOC50003>) is weakly conserved among the BEACH proteins and does not share any recognizable sequence similarity with other PH domains. The structural organization of these three domains is highly conserved across all known BEACH domain containing proteins (BDCPs) and might function as an independent cassette within these proteins. Therefore, this region is referred to as the PH-BEACH-WD40 (PBW) module [1,2,3].

The BEACH-type PH domain contains a seven-stranded, antiparallel β-sandwich (β1-β7) and an α helix (α3) near its C terminus (see <PDB:1T77>). This is the typical fold of canonical PH domains, although the PH domains of BEACH proteins share no sequence similarity with these other PH domain. Another feature of the BEACH-type PH domain is the presence of two small helices (α1 and α2) in the loop between strands β3 and β4. These helices partially block the binding site for phospholipid and phosphotyrosine in the other PH domains and suggest that the BEACH-type PH domain may have a different function [1,2].

Some proteins known to contain a PH BEACH-type domain are listed below:

• Human lysosomal trafficking regulator or Chediak-Higashi Syndrome (CHS) protein. Defects in the CHS protein are the cause of Chediak-Higashi Syndrome, a rare autosomal disorder characterized by hypopigmentation, severe immunologic deficiency, a bleeding tendency and neurologic abnormalities. As an important hallmark of several tissues derived from CHS patients is the occurrence of giant inclusion bodies and organelles and protein sorting defects in these organelles, the CHS protein is thought to be involved in vesicle fusion or fission. The CHS protein contains 7 WD- repeats. The mouse ortholog of CHS is called 'beige'.
• Mammalian FAN (Factor Associated with Neutral-sphingomyelinase activation). It binds to the N-SMase activation domain (NSD) of the p55 TNF-receptor and mediates the activation of N-SMase after ligand binding. FAN contains five WD-repeats.
• Human lipopolysaccharide-responsive and beige-like anchor protein (LBA) (also known as Beige like protein or CDC4-like protein). It may have a function in in polarized vesicle trafficking, and is localized to vesicles after stimulation by lipopolysaccharide (LPS).
• Vertebrate neurobeachin (Nbea). It has been implicated in membrane traffic in neuronal cells.
• Caenorhabditis elegans hypothetical proteins F52C9.2 and F52C9.3.
• Yeast hypothetical protein YCR032W.

The profile we developed covers the entire PH BEACH-type domain.