Nielsen K L, Sottrup-Jensen L, Nagase H, Thøgersen H C, Etzerodt M
Department of Chemistry, University of Aarhus, Denmark.
DNA Seq. 1994;5(2):111-9. doi: 10.3109/10425179409039712.
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.
通过cDNA和部分肽序列分析，已确定母鸡卵巨球蛋白（卵抑素）亚基的完整氨基酸序列。卵抑素是α-巨球蛋白（αM）蛋白质家族的四聚体成员。4715 nt的卵抑素cDNA编码一个36或16个残基的信号肽和一个1437个残基的成熟蛋白（162.2 kDa）。在蛋白质水平上，卵抑素与哺乳动物αM之间的序列同一性总体得分是39%-44%，表明其与导致哺乳动物αM的谱系早期分化。每个亚基的卵抑素含有56摩尔的氨基葡萄糖，其12个天冬酰胺残基可能被N-糖基化。包括碳水化合物在内，卵抑素亚基的大小约为185 kDa。预计卵抑素亚基含有12个链内二硫键，预计两个亚基通过两个链间桥由二硫键连接。一个半胱氨酸残基可能未配对，或作为第三个链间二硫键参与二聚体形成。卵抑素含有一个独特的40个残基的诱饵区域。与其他αM不同，由于半胱氨酸被天冬酰胺取代（TGC或TGT变为AAT），卵抑素不含有内部β-半胱氨酸-γ-谷氨酸硫酯，但硫酯的谷氨酰胺部分得以保留。通过比较αM中受体结合域的序列与卵抑素的相应区域，提出了哺乳动物αM受体识别的可能决定因素。
