The transforming growth factor (TGF)-β family is a group of structurally related, multifunctional growth factors, or ligands that are crucially involved in the development, regulation, and maintenance of animal tissues. In humans, the family counts over 33 members. These secreted ligands typically form multimeric complexes with two type I and two type II receptors to activate one of two distinct signal transduction branches. A striking feature of the family is its promiscuity, i.e., many ligands bind the same receptors and compete with each other for binding to these receptors. Although several explanations for this feature have been considered, its functional significance has remained puzzling. However, several recent reports have promoted the idea that ligand-receptor binding promiscuity and competition are critical features of the TGF-β family that provide an essential regulating function. Namely, they allow a cell to read and process multi-ligand inputs. This capability may be necessary for producing subtle, distinctive, or adaptive responses and, possibly, for facilitating developmental plasticity. Here, we review the molecular basis for ligand competition, with emphasis on molecular structures and binding affinities. We give an overview of methods that were used to establish experimentally ligand competition. Finally, we discuss how the concept of ligand competition may be fundamentally tied to human physiology, disease, and therapy.

转化生长因子 (TGF)-β 家族是一组结构相关的多功能生长因子或配体，它们在动物组织的发育、调节和维持中起着至关重要的作用。在人类中，家庭成员超过 33 人。这些分泌的配体通常与两种 I 型和两种 II 型受体形成多聚体复合物，以激活两个不同的信号转导分支之一。家庭的一个显着特征是它的滥交，即，许多配体结合相同的受体并相互竞争结合这些受体。尽管已经考虑了对该特征的多种解释，但其功能意义仍然令人费解。然而，最近的几份报告提出了这样一种观点，即配体-受体结合的混杂和竞争是 TGF-β 家族的关键特征，提供了重要的调节功能。即，它们允许细胞读取和处理多配体输入。这种能力可能是产生微妙、独特或适应性反应所必需的，并且可能是促进发育可塑性所必需的。在这里，我们回顾了配体竞争的分子基础，重点是分子结构和结合亲和力。我们概述了用于建立实验性配体竞争的方法。最后，