bep4

Function

bep4 is a member of a multigenic family, coding for butanol-extractable proteins.
In sea urchin embryos butanol treatment extracts cell surface proteins including the constituents of a 22S particle called toposome, which is believed to play a role in cell interactions.
bep4 is a single-copy gene (Di Carlo et al., 1990).

Protein

bep4 is a butanol-extractable protein. bep4 contain open reading frame coding for 307 amino acids.
Within the coding region there are two domains (A and B) and one specific central region. The A region code for 68 aa, the B part contain 106 amino acids, the specific region can codify for 95 amino acids.
By amino acid analysis it is possible to observe that A and B regions are hydrophobic. Moreover, the presence of two Cys in both of these regions allows to suppose that the two parts might interact and build a highly hydrophobic zone to be anchored at the plasma membrane to the interaction between both parts (Di Carlo et al., 1990).
The deduced amino acid sequence contains two possible Ca²⁺-binding motifs. The cluster of type DXD(N)XD(N) is very frequent in many EF-hand domains (Tufty and Kretsinger, 1975). This cluster is necessary for the coordination of Ca²⁺ ions by side chain oxygen atoms in the Ca²⁺- binding sites. The aa of these motifs form a loop structure in which the ligands residues are located (Tuffy and Kretsinger, 1975).
The possibility that the bep4 protein can bind Ca²⁺ may be important for its function, which has been demonstrated to play a role in cell-cell interaction (Romancino et al., 1992).
GenBank: 321051

Subcellular location

bep4 presumably belongs to cell surface proteins (Di Carlo et al., 1990).

Expression Pattern

Northern blot analysis showed that bep4 is transcribed during oogenesis into mRNA of 1.4 kb, which is stored in egg and utilized during early embryogenesis. The highest intensity of the band is observed in ovary and in egg RNA. The signal reduction is observed from 32 cell stage.
This RNA is not detectable after the gastrula stage (Di Carlo et al., 1990).
bep4 maternal messenger is localized in the animal part of P. lividus egg and embryos. It was demonstrated that bep4 mRNA is associated with the cytoskeleton element and that this association is necessary for the localization (Romancino et al., unpublished results).
The spatial distribution of bep4 protein in eggs and embryos was established by whole mount immunohistochemistry. This protein is located in the animal part of unfertilized and fertilized eggs; thereafter it is much less represented in structures derived from the vegetal cells of the embryo such as the micromeres of the 16 cell stage, the primary mesenchyme of blastula and the gut of gastrula. At the prism stage bep4 protein is present to some ectodermal parts and thereafter, at the pluteus stage, to the oral region (Romancino et al., 1998).

mRNA level

Temporal accumulation
Method: Nothern blot analysis
Reference: Di Carlo et al., 1990

Stage	Egg	32 cells	Morula	Blastula	Gastrula	Prism	Pluteus
Level	+ +	+ +	+	+	+ -	-	-

Sequences

GenBank:

partial cds

Regulatory Regions

Regions

Regulatory Connections

Upstream Genes

LP54 (54-kDa protein)
bep4

Downstream Genes

Evolutionary Homologues

bep4 Spherechinus granularis

Links

Urchin Web

Bibliography

UrchiNet

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