Allosteric Effects

别构效应

The interactions between biological molecules often depend upon the shape and structure of those molecules which provide locations for binding and interaction. Many interactions depend upon enzymes, and the action of those enzymes in stimulating or inhibiting some biological reaction can be affected by another compound that binds to a different part of the enzyme. Such a compound is called an allosteric effector. Such an effector can cause changes in the shape of the enzyme and modify its function.

生物分子之间的相互作用往往取决于这些分子的形状和结构，这些结构提供了结合和相互作用的位点。许多相互作用依赖于酶，而这些酶的作用——刺激或抑制某些生物反应——可能受到另一种化合物的影响，该化合物结合在酶的不同部位。这种化合物被称为别构效应剂。这样的效应剂可以引起酶形状的变化并改变其功能。

An example of an allosteric effect is the cooperative binding of oxygen to hemoglobin. In that case the binding of one oxygen to the hemoglobin makes it easier for the second and subsequent oxygens to bind. In this case the oxygen molecule is the ligand and the allosteric effector.

一个典型的别构效应是血红蛋白对氧的协同结合。在这种情况下，一个氧分子结合到血红蛋白上，使第二个及后续的氧分子更容易结合。在此情况下，氧分子是配体，而别构效应剂是血红蛋白。

Ligands

配体

In the case of allosteric effects on the activity of a biological compound, the effect may be initiated by the binding of another compound which is termed a "ligand". In the example of the cooperative binding of oxygen to hemoglobin, the oxygen molecule is the ligand.

在生物化合物活性的别构效应中，效应可能由另一种化合物的结合引发，这种化合物被称为‘配体’。在血红蛋白氧合作用的示例中，氧分子就是配体。

A ligand can be any molecule or atom or ion thereof that binds reversibly to a protein. Ligands can travel in the fluids of the body, in blood, tissues or the cytoplasm of a cell. When a ligand binds to a protein, the protein undergoes a conformational change. Such changes in the overall shape of the protein can trigger many kinds of actions. The reversible binding of the ligand means that it can have an effect for a period of time and then be recycled without being changed. This allows ligands to act as messengers.

配体可以是任何分子、原子或离子，它们可以可逆地与蛋白质结合。配体可以在体液中移动，如血液、组织或细胞的细胞质中。当配体与蛋白质结合时，蛋白质会发生构象变化。这种蛋白质整体形状的变化可以引发多种作用。配体可逆的结合意味着它可以在一段时间内起作用，然后被回收而不发生改变。这使得配体能够作为信使发挥作用。

An example of the use of a ligand is the excitation of a muscle fiber by the use of the ligand acetylcholine. When a nerve signal reaches a muscle fiber, the reception of the neurotransmitter acetylcholine in the synapse acts as a ligand-gated sodium channel to initiate the process of contraction of the muscle fiber.

使用配体的一个例子是通过配体乙酰胆碱来激发肌肉纤维。当神经信号到达肌肉纤维时，突触中乙酰胆碱作为配体门控的钠通道起作用，从而引发肌肉纤维收缩的过程。