Cloning characterisation and expression of a G-protein-couple receptor from Lymnaea stagnalis and identification of a leucokinin-like peptide PSFHSWSamide as its endogenous ligand

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The Lymnaea Cardioexcitatory Peptide (LyCEP) Receptor: A G-Protein–Coupled Receptor for a Novel Member of the RFamide Neuropeptide Family

A novel G-protein–coupled receptor (GRL106) resembling neuropeptide Y and tachykinin receptors was cloned from the molluscLymnaea stagnalis. Application of a peptide extract from the Lymnaea brain to Xenopus oocytes expressing GRL106 activated a calcium-dependent chloride channel. Using this response as a bioassay, we purified the ligand for GRL106,Lymnaea cardioexcitatory peptide (LyCEP), an RFamide-type decapeptide (TPHWRPQGRF-NH2) displaying significant similarity to the Achatina cardioexcitatory peptide (ACEP-1) as well as to the recently identified family of mammalian prolactin-releasing peptides. In the Lymnaeabrain, the cells that produce egg-laying hormone are the predominant site of GRL106 gene expression and appear to be innervated by LyCEP-containing fibers. Indeed, LyCEP application transiently hyperpolarizes isolated egg-laying hormone cells. In theLymnaea pericardium, LyCEP-containing fibers end blindly at the pericardial lumen, and the heart is stimulated by LyCEPin vitro. These data confirm that LyCEP is an RFamide ligand for GRL10

The T4-encoded cochaperonin, gp31, has unique properties that explain its requirement for the folding of the T4 major capsid protein

The morphogenesis of bacteriophage T4 requires a specialized bacteriophage-encoded molecular chaperone (gp31) that is essential for the folding of the T4 major capsid protein (gp23). gp31 is related to GroES, the chaperonin of the Escherichia coli host because it displays a similar overall structure and properties. Why GroES is unable to fold the T4 capsid protein in conjunction with GroEL is unknown. Here we show that gp23 binds to the GroEL heptameric ring opposite to the ring that is bound by gp31 (the so-called trans-ring), while no binding to the trans-ring of the GroEL-GroES complex is observed. Although gp23 can be enclosed within the folding cage of the GroEL-gp31 complex, encapsulation within the GroEL-GroES complex is not possible. So it appears that folding of the T4 major capsid protein requires a gp31-dependent cis-folding mechanism likely inside an enlarged “Anfinsen cage” provided by GroEL and gp31

Stp1p, Stp2p and Abf1p are involved in regulation of expression of the amino acid transporter gene BAP3 of Saccharomyces cerevisiae

Expression of the BAP3 gene of Saccharomyces cerevisiae, encoding a branched chain amino acid permease, is induced in response to the availability of several naturally occurring amino acids in the medium. This induction is mediated via an upstream activating sequence (called UAS(aa)) in the BAP3 promoter, and dependent on Stp1p, a nuclear protein with zinc finger domains, suggesting that Stp1p is a transcription factor involved in BAP3 expression. In this paper, we show that Stp2p, a protein with considerable similarity to Stp1p, is also involved in the induction of BAP3 expression. To gain more insight into the roles of STP1 and STP2, we have overexpressed both Stp1p and Stp2p in yeast cells. Gel shift assays with the UAS(aa) as a probe show that the UAS(aa) can form two major complexes. One complex is dependent on Stp2p overexpression and the other is formed independently of STP1 or STP2, suggesting that the UAS(aa) is also bound by another factor. Here we show that the other factor is Abf1p, which binds specifically to the UAS(aa) of BAP3