Tizzano Marco, Sbarbati Andrea
Department of Morphological-Biomedical Sciences, Section of Anatomy and Histology, University of Verona, Strade le Grazie, 8, 37134 Verona, Italy.
Med Hypotheses. 2006;67(3):513-6. doi: 10.1016/j.mehy.2006.03.010. Epub 2006 Apr 27.
Bacteria are known to regulate diverse physiological processes through a mechanism called quorum sensing (QS). Prokaryotes communicate by extracellular signalling compounds, i.e. autoinducers (acyl homoserine lactone, AHL of Gram negative bacteria) or pheromones (post-translationally modified peptides of Gram positive bacteria), which activate genetic pathways when they reach a sufficient concentration (QS). A large number of Gram-negative quorum-sensing systems studied so far utilize N-acyl homoserine lactones as signal molecules. In vertebrates small synthetic molecules called growth hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. GH release is stimulated by hypothalamic GH-releasing hormone (GHRH) and ghrelin (endogenous ligand of the GHS-receptor, GHS-R). Ghrelin is a 28-amino acid peptide, in which the serine-3 (Ser3) is n-octanoylated, and this modification is essential for ghrelin's activity. Ghrelin is the first known case of a peptide hormone modified by a fatty acid. The major active form of ghrelin is a 28-amino acid peptide with octanoylated Ser3; one of the more represented bacterial autoinducers is the N-Octanoyl-DL-homoserine lactone (C8-HL) molecule. The authors hypothesize that Gram-negative bacteria and vertebrates have a functional similarity in the search of food and an important structural homology of AHL and ghrelin for the highly conserved Serine-acylated motive in both molecules. Our suggestions could help one to understand the convergent origin and the biologic meaning of the Serine-acylated group in these organisms, a biologic meaning very important due to the high conservation in two kingdoms which are so different.
已知细菌通过一种称为群体感应（QS）的机制来调节多种生理过程。原核生物通过细胞外信号化合物进行通讯，即自诱导物（革兰氏阴性菌的酰基高丝氨酸内酯，AHL）或信息素（革兰氏阳性菌翻译后修饰的肽），当它们达到足够浓度时会激活遗传途径（群体感应）。迄今为止研究的大量革兰氏阴性群体感应系统利用N-酰基高丝氨酸内酯作为信号分子。在脊椎动物中，称为生长激素促分泌素（GHSs）的小合成分子刺激垂体释放生长激素（GH）。生长激素的释放受到下丘脑生长激素释放激素（GHRH）和胃泌素（GHS受体GHS-R的内源性配体）的刺激。胃泌素是一种28个氨基酸的肽，其中丝氨酸-3（Ser3）被正辛酰化，这种修饰对于胃泌素的活性至关重要。胃泌素是第一个已知的被脂肪酸修饰的肽激素。胃泌素的主要活性形式是具有辛酰化Ser3的28个氨基酸的肽；其中一种更具代表性的细菌自诱导物是N-辛酰-DL-高丝氨酸内酯（C8-HL）分子。作者推测，革兰氏阴性细菌和脊椎动物在寻找食物方面具有功能相似性，并且AHL和胃泌素在这两种分子中高度保守的丝氨酸酰化基序具有重要的结构同源性。我们的建议可能有助于人们理解这些生物体中丝氨酸酰化基团的趋同起源和生物学意义，由于在这两个差异很大的王国中高度保守，这种生物学意义非常重要。
