Between Av1 molecules and Av2 molecules, there are two or more than two binding sites among which possesses a positive cooperative effect, namely the effect between the Avl-Av2 binding sites and the acetylene reduction active sites.

• Av1与Av2之间有两个或两个以上的结合部位；这些结合部位之间存在着正协同效应；Av1与Av2的结合部位对乙炔还原活性部位有正协同效应.