Johnston R N, Shaw C, Halton D W, Verhaert P, Baguna J
Comparative Neuroendocrinology Research Group, School of Clinical Medicine, Queen's University of Belfast, Northern Ireland.
Biochem Biophys Res Commun. 1995 Apr 17;209(2):689-97. doi: 10.1006/bbrc.1995.1554.
Modern phylogenetic schemes propose a free-living turbellarian-like organism as the ancestor of all Bilateria, including chordates. While neuropeptides are now known to be of ancient origin within the nervous systems of invertebrates, the neuropeptides of turbellarians remain virtually unexplored. Here we report the primary structure of an FMRFamide-related pentapeptide, Gly-Tyr-Ile-Arg-Phe amide (GYIRFamide), isolated from an acidified ethanolic extract of the aquatic triclad turbellarian, Dugesia tigrina. Previously, we reported the primary structure, RYIRFamide, from the New Zealand terrestrial turbellarian, Artioposthia triangulata, widely regarded as a most atypical species. However, the present data implies a high degree of primary structural conservation between the FMRFamide-related peptides of both species despite the zoogeographical isolation of the New Zealand form for several hundred million years. In addition, while authentic FMRFamide itself has been identified in many molluscs and a few annelids, the current data would suggest that turbellarian analogues are typically pentapeptides with an X-Y-I-R-Famide motif. A protein/peptide database search revealed that the sequence GYIRF is contained within the primary structure of several bacterial Ni/Fe hydrogenase B-type cytochrome subunits and several proliferating cell nuclear antigens (cyclins) from plants.
现代系统发育学方案提出，一种类似自由生活涡虫的生物是所有两侧对称动物（包括脊索动物）的祖先。虽然现在已知神经肽在无脊椎动物神经系统中起源古老，但涡虫的神经肽实际上仍未得到充分研究。在此，我们报告了从水生三肠目涡虫——虎纹三角涡虫的酸化乙醇提取物中分离出的一种与FMRF酰胺相关的五肽——甘氨酸 - 酪氨酸 - 异亮氨酸 - 精氨酸 - 苯丙氨酸酰胺（GYIRF酰胺）的一级结构。此前，我们报道了来自新西兰陆生涡虫——三角无刺涡虫的一级结构RYIRF酰胺，该物种被广泛认为是一种非常特殊的物种。然而，目前的数据表明，尽管新西兰的这种涡虫在动物地理学上已隔离了数亿年，但这两个物种与FMRF酰胺相关的肽在一级结构上仍高度保守。此外，虽然在许多软体动物和少数环节动物中已鉴定出真正的FMRF酰胺本身，但目前的数据表明涡虫类似物通常是具有X - Y - I - R - F酰胺基序的五肽。蛋白质/肽数据库搜索显示，序列GYIRF包含在几种细菌镍/铁氢化酶B型细胞色素亚基以及几种植物增殖细胞核抗原（细胞周期蛋白）的一级结构中。
