Büllesbach E E, Schwabe C, Lacy E R
Department of Biochemistry, Medical University of South Carolina, Charleston 29425, USA.
Biochemistry. 1997 Sep 2;36(35):10735-41. doi: 10.1021/bi970393n.
The alkaline gland fluid of the Atlantic stingray (Dasyatis sabina) contains a molecule that cross-reacts weakly to anti-porcine relaxin antibodies. This material was isolated and purified to homogeneity by reversed-phase high-performance liquid chromatography. In SDS gel electrophoresis, the molecule showed an apparent molecular mass of 13 kDa which upon reduction formed two polypeptide chains of 4 and 9 kDa, respectively. Sequence analyses revealed a 27-amino acid residue A chain and a 54-amino acid residue B chain which contained an N-glycosylation site in position B37. The distribution of the six cysteines and possibly the disulfide bonding is identical to that found in insulins and most relaxins. Although the stingray relaxin-like molecule contains the structurally relevant glycine residues within the A chain, in the midregion of the B chain it has only one of the two requisite binding site arginines, which explains the lack of relaxin bioactivity in standard mammalian assays. Stingray relaxin is the first member of the relaxin family identified in a nonhomeotherm male. Carbohydrate analysis of relaxin revealed an N-linked asialo, agalacto, bisected biantennary, and a core-fucosylated oligosaccharide in the position of Asn B37 which makes it the first reported glycosylated relaxin-like molecule.
大西洋黄貂鱼（Dasyatis sabina）的碱性腺液中含有一种与抗猪松弛素抗体发生弱交叉反应的分子。该物质通过反相高效液相色谱法分离纯化至同质。在SDS凝胶电泳中，该分子的表观分子量为13 kDa，还原后分别形成4 kDa和9 kDa的两条多肽链。序列分析显示，A链有27个氨基酸残基，B链有54个氨基酸残基，B链的B37位含有一个N-糖基化位点。六个半胱氨酸的分布以及可能的二硫键与胰岛素和大多数松弛素中的相同。尽管黄貂鱼松弛素样分子在A链中含有结构相关的甘氨酸残基，但在B链的中部区域它只有两个必需结合位点精氨酸中的一个，这解释了在标准哺乳动物检测中缺乏松弛素生物活性的原因。黄貂鱼松弛素是在非恒温动物雄性中鉴定出的松弛素家族的第一个成员。对松弛素的碳水化合物分析显示，在Asn B37位置存在一个N-连接的去唾液酸、去半乳糖、双叉双天线和核心岩藻糖基化寡糖，这使其成为首个报道的糖基化松弛素样分子。
