A nonsteroidal regulator, composed of two covalently linked inhibin beta-B subunits (sometimes known as activin beta-B or activin/inhibin beta-B).
Source:
GOC:go_curators
Comment
Note that the actions of the activin complex are the opposite of those of the inhibin complex, which is a dimer of an inhibin beta-A or inhibin beta-B subunit and a inhibin alpha subunit. See 'inhibin complex ; GO:0043511'.