Since a crucial portion of the receptor-binding site in LH and FSH p subunits is different, and possession of both enables binding to both LH and FSH receptors, these hormones may occupy in their receptors with a slightly different orientation. The orientation of LH in its receptor permits engagement of the positively charged determinant loop. The slightly different orientation of FSH in its receptor permits engagement of its FSH determinant. As the determinant loop of eLH/CGp is closer to the aAsn56 oligosaccharide, it is subject to a greater degree of steric hindrance by this carbohydrate—hence the greater magnitude of the influence of this structure on FSH receptor binding. buy flovent inhaler
Since the FSH determinant is slightly further away, steric hindrance by the carbohydrate is reduced. This hypothesis is attractive, as it could be tested in a very straightforward manner by combining equine gonadotropin a-subunit preparations with oLHp and hFSHp. Combination of equine a-subunit preparations with oLHp should result in hybrids that differ significantly in their LH receptor-binding activities, while association with hFSHp should provide hybrid FSH preparations that exhibit small differences in FSH receptor-binding activity.