Amino Acid Sequence of Hen Ovomacroglobulin (Ovostatin) deduced from cloned cDNA

Abstract

The complete amino acid sequence of the hen ovomacroglobulin (ovostatin) subunit has been determined from cDNA and partial peptide sequence analysis. Ovostatin is a tetrameric member of the alpha-macroglobulin (alpha M) family of proteins. The 4715 nt ovostatin cDNA encodes a 36- or a 16-residue signal peptide and a 1437-residue mature protein (162.2 kDa). At the protein level the overall score of sequence identity between ovostatin and mammalian alpha Ms is 39-44%, indicating an early divergence from the line leading to the mammalian alpha Ms. Ovostatin contains 56 mol glucosamine per mol subunit, and 12 of its Asn-residues are likely to be N-glycosylated. Including carbohydrate, the size of the ovostatin subunit is approx. 185 kDa. The ovostatin subunit is predicted to contain 12 intrachain disulfide bridges, and two subunits are predicted to be disulfide bound by two interchain bridges. One Cys residue may be unpaired or participate in dimer formation as a third interchain disulfide bridge. Ovostatin contains a unique 40-residue bait region. In contrast to other alpha Ms, ovostatin contains no internal beta-Cys-gamma-Glu thiol ester, as a result of a Cys-to-Asn replacement (TGC or TGT to AAT), but the Gln-moiety of the thiol ester is preserved. By comparing the sequences of the receptor binding domain in alpha Ms with the corresponding region of ovostatin possible determinants for receptor recognition of mammalian alpha Ms are proposed.

A New Assessment of Thioester-Containing Proteins Diversity of the Freshwater Snail Biomphalaria glabrata

“…Such replacement of the cysteine residue by a serine was also reported for tsetse fly TEP2, an iTEP of which the expression is particularly up-regulated in the salivary gland following Trypanosoma brucei infection [69]. The replacement of cysteine residue in the thioester site was also evidenced for chicken ovostatin [70], without alteration of its proteinase-inhibitor activity [71]. The absence of thioester site in the BgMCRs and two of the three BgC3 suggests that these molecules cannot covalently bind to microbe surface, but that does not mean that they are not functional.…”

Identification of Residues in α-Macroglobulins Important for Binding to the α2-Macroglobulin Receptor/Low Density Lipoprotein Receptor-related Protein

“…The selection of residues for mutagenesis studies was based on comparison of the primary structures of the receptor binding domains of nine known receptor binding macroglobulins with the recently determined sequence of the nonbinding hen ovoM (32). As is evident from Fig.…”

Simple Two-step Chromatographic Method for Purification of Ovomacroglobulin

“…Identification of ovomacroglobulin: The sample of purified ovomacroglobulin was identified by liquid chromatography-electrospray ionization-linear ion trap mass spectrometry. One hundred fourteen unique peptides were generated and the accepted amino acids residues was 923, corresponding to the total 1457 amino acids residues of ovomacroglobulin, the sequence coverage rate was 63.34 % 14 . After retrieving and comparing in database, the protein was identified as ovostatin/ ovomacroglobulin (Gallus gallus).…”

“…Ovomacroglobulin can inhibit the generation of bradykinin through preventing bacterial protease activates Hageman factor-kinin system 12 . More noteworthy, ovomacroglobulin are highly homologous with α2-macroglobulin (α2M) [13][14][15] , so, it may be it has more important biological activities that like α2M.…”