PHOSPHOLIPASE C, BETA-4; PLCB4
Phospholipase C (PLC) catalyzes hydrolysis of a plasma membrane phospholipid, phosphatidylinositol 4,5-bisphosphate, generating 2 second messengers, the water soluble 1,4,5-inositol trisphosphate and the membrane-associated 1,2-diacylglycerol. In mammalian tissues, several groups of PLCs have been characterized, including PLC-beta, and each group contains at least 3 isoforms. These proteins are single polypeptides, ranging in molecular mass from 65 to 154 kD (review by Alvarez et al., 1995) .
Phosphatidylinositol-specific phospholipase C (EC 22.214.171.124), a eukaryoticintracellular enzyme, plays an important role in signal transduction processes (PUBMED:1849017). It catalyzes the hydrolysis of 1-phosphatidyl-D-myo-inositol-3,4,5-triphosphate into the second messenger molecules diacylglycerol and inositol-1,4,5-triphosphate. This catalytic process is tightly regulated by reversible phosphorylation and binding of regulatory proteins (PUBMED:1419362), (PUBMED:1319994), (PUBMED:1335185). In mammals, there are at least 6 different isoforms of PI-PLC, they differ in their domain structure, their regulation, and their tissue distribution. Lower eukaryotes also possess multiple isoforms of PI-PLC. All eukaryotic PI-PLCs contain two regions of homology, sometimes referred to as the 'X-box' and 'Y-box'. The order of these two regions is always the same (NH2-X-Y-COOH), but the spacing is variable. In most isoforms, the distance between these two regions is only 50-100 residues but in the gamma isoforms one PH domain, two SH2 domains, and one SH3 domain are inserted between the two PLC-specific domains. The two conserved regions have been shown to be important for the catalytic activity. By profile analysis, we could show that sequences with significant similarity to the X-box domain occur also in prokaryotic and trypanosome PI-specific phospholipases C. Apart from this region, the prokaryotic enzymes show no similarity to their eukaryotic counterparts
Phosphoinositide-specific phospholipase C, efhand-like
Members of this family are predominantly found in phosphoinositide-specific phospholipase C. They adopt a structure consisting of a core of four alpha helices, in an EF like fold, and are required for functioning of the enzyme .
Cloning and characterization of the human phosphoinositide-specific phospholipase C-beta 1 (PLC beta 1).
Four mammalian isozymes are known (PLCβ1–4), which differ in their function and expression patterns in vivo. We have characterized the human PLCβ1 genomic locus (PLCβ1), cloned two distinct PLCβ1 cDNAs (PLCβ1a and b) and analysed their respective expression patterns in a comprehensive panel of human tissues using quantitative TaqMan technology. The two cDNAs derive from transcripts generated through alternative splicing at their 3′ end, and are predicted to encode for PLCβ1 isoforms differing at their carboxy-terminus. The human PLCβ1 isoforms are co-expressed in the same tissues with a distinctly CNS-specific profile of expression. Quantitative differences in PLCβ1 isoform expression levels are observed in some tissues. Transient expression of epitope-tagged versions of the two isoforms followed by immunofluorescence revealed localization of the proteins to the cytoplasm and the inner side of the cell membrane. Finally, we characterized the structure of the PLCβ1 locus and confirmed its mapping to human chromosome 20 .
- ↑ http://www.ncbi.nlm.nih.gov/omim/600810
- ↑ http://pfam.sanger.ac.uk/family/PF09279.4
- ↑ Andrea Caricasole, Cinzia Sala, Renza Roncarati, Elisa Formenti, Georg C. Terstappen, Cloning and characterization of the human phosphoinositide-specific phospholipase C-beta 1 (PLC[beta]1), Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression, Volume 1517, Issue 1, 15 December 2000, Pages 63-72, ISSN 0167-4781, DOI: 10.1016/S0167-4781(00)00260-8.fckLR(http://www.sciencedirect.com/science/article/B6T1V-41WBB32-7/2/c29bb149393824b8e3937b51c705b85e)