Yang JC and Hedrick JL (1997), cDNA cloning and sequence analysis of the Xenop...

XB-ART-16141

Dev Growth Differ 1997 Aug 01;394:457-67. doi: 10.1046/j.1440-169x.1997.t01-3-00007.x.

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cDNA cloning and sequence analysis of the Xenopus laevis egg envelope glycoprotein gp43.

Yang JC , Hedrick JL .

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The glycoproteins of the Xenopus laevis egg envelope function in fertilization and development. As the unfertilizable coelomic egg transits the pars recta region of the oviduct, it is converted to a fertilizable egg by limited proteolysis of the envelope glycoprotein gp43 to gp41. This conversion is caused by an oviductally secreted serine active site protease, oviductin. We cloned a cDNA for gp43 from an oocyte cDNA library. The cDNA encoded a 454 amino acid protein homologous to the ZPC family of glycoproteins previously shown to be present in mammalian and fish egg envelopes. Conserved ZPC domains and motifs present in the Xenopus sequence included a signal peptide sequence, an N-linked glycosylation site, and 12 aligned Cys residues. In mammalian and Xenopus sequences, a furin-like (convertase) site and a C-terminal transmembrane domain were present reflecting the biosynthesis of ZPC in these species via the secretory glycoprotein pathway. However, fish envelope glycoproteins lack these sequences since they are synthesized via a different route (in the liver, transported to the ovary, and assembled into the egg envelope surrounding the oocyte). Consensus amino acid residues were identified by sequence comparisons of seven ZPC family members; 19% of the amino acid residues were invariant and 48% of the residues were identical in at least four of the seven sequences. The consensus sequence was used to make structure-fertilization function predictions for this phylogenetically conserved family of glycoproteins.

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Species referenced: Xenopus laevis
Genes referenced: furin gcg zp3 zp3

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	Fig.1. Nucleotide and deduced amino acid sequence of Xenopus /aevis gp43. The nucleotides are numbered from the first determined nucleotide at the 5' untranslated end. The initiation and termination codons are in bold and the polyadenylation site is overlined. The 1362 nt open reading frame is translated into the ZPC polypeptide in the second line. The amino acids are numbered from the start methionine. A 21 amino acid signal peptide is indicated by underlined amino acids and the signal peptidase cleavage site (Aia21-Giu22) by a solid arrow head. TheN-terminal amino acid sequence (Leu57 -Cys69)and an internal amino acid sequence (lle254- Lys264) determined by Edman sequencing of the expressed protein and an isolated peptide are indicated with solid lines. Two potential N-linked glycosylation sites are indicated by double underlines. Potential furin-like cleavage site residues are indicated with a heavy underline and a putative transmembrane domain with a dotted line.
	Fig. 2. Tissue specific expression of ZPC mRNA. Northern blotting experiments using RNA isolated from various tissues and 32P-Iabeled eDNA were carried out as described in the text.
	Fig. 3. Alignment of ZPC glycoprotein sequences. Sequences were aligned with the GCG PILEUP program (gapweight = 3.0, gaplengthweight = 0.1) and a consensus sequence generated using the GCG PRETIY program.
	Fig. 4. Consensus and conserved sequences of ZPC glycoproteins. The consensus sequence required that 4/7 sequences have identical residues The conserved sequence required that 7/7 sequences have identical residues. Aligned residue numbering is the same as in Fig. 2. Symbols used are: 00, Cys; 'Y, convertase or turin-like cleavage site;~. transmembrane region;*· N-linked glycosylation site.