Giannella R A
Division of Digestive Diseases, University of Cincinnati College of Medicine, OH 45267-0595.
J Lab Clin Med. 1995 Feb;125(2):173-81.
STa represents a family of homologous heat-stable peptide toxins that are elaborated by a variety of bacteria capable of causing enteric disease in human beings. All these peptides have a tertiary structure, maintained by disulfide bridges, which is required for receptor occupancy and biologic activity. The toxins have highly homologous carboxy-terminal domains and variable differences at the amino-terminal domain. The amino-terminal domain of these various peptides is not required for biologic activity. Recently an endogenous ligand called guanylin has been extracted from mammalian intestine and shown to bind the STa receptor. A similar peptide, called uroguanylin, has been found in human and animal urine. It is likely that guanylin and uroguanylin are indeed endogenous ligands for the STa receptor and may be modulators of Cl- secretion in the intestine, kidney, and perhaps in other organs. The STa-guanylin receptors are located on enterocytes, colonocytes, and various extraintestinal tissues. These receptors are one of a family of transmembrane guanylate cyclases that have homologous intracytoplasmic domains but divergent extracellular domains. It is likely that the extracellular domains of these various receptor cyclases confer specificity for ligand binding. Although GC-C, the STa receptor, may also be a receptor for guanylin, other receptors may exist that may be more specific for guanylin.(ABSTRACT TRUNCATED AT 250 WORDS)
耐热肠毒素（STa）代表一类同源的热稳定肽毒素，由多种可导致人类肠道疾病的细菌产生。所有这些肽都具有由二硫键维持的三级结构，这是占据受体和发挥生物活性所必需的。这些毒素具有高度同源的羧基末端结构域，而氨基末端结构域存在可变差异。这些不同肽的氨基末端结构域对于生物活性并非必需。最近，一种名为鸟苷素的内源性配体已从哺乳动物肠道中提取出来，并显示能与STa受体结合。在人和动物尿液中发现了一种类似的肽，称为尿鸟苷素。鸟苷素和尿鸟苷素很可能确实是STa受体的内源性配体，并且可能是肠道、肾脏以及或许其他器官中氯离子分泌的调节剂。STa - 鸟苷素受体位于肠上皮细胞、结肠细胞和各种肠外组织上。这些受体是跨膜鸟苷酸环化酶家族的成员之一，它们具有同源的胞质内结构域，但胞外结构域不同。很可能这些不同受体环化酶的胞外结构域赋予了配体结合的特异性。尽管STa受体GC - C也可能是鸟苷素的受体，但可能存在对鸟苷素更具特异性的其他受体。（摘要截短于250字）
