A, Model showing processing of AMH and assembly of the AMH receptor signaling complex. The AMH precursor must be cleaved to bind AMHRII and after binding the proregion domain dissociates from the mature domain. B, Biochemical analysis of AMH in control samples containing different ratios of uncleaved and cleaved AMH. Samples were prepared with various ratios of recombinant s-AMH (secreted AMH containing ∼95% uncleaved AMH precursor and ∼5% cleaved AMH) and c-AMH (100% cleaved AMH) in either FF or female serum with a total AMH level below 1 ng/mL; all samples contained the same level of total AMH (50 ng/mL). AMH was captured with an anti-N-terminal AMH mAb (10.6) conjugated to Sepharose, analyzed by SDS-PAGE under reducing conditions, followed by Western blotting using an anti-AMH polyclonal Ab. The level of AMH cleavage in each sample was calculated from a densitometry analysis (Image J) of the bands corresponding to the AMH precursor (70 kDa) and the N-terminal AMH proregion obtained after cleavage (58 kDa). The percentage of cleavage (proregion/[proregion + precursor] × 100) is shown at the bottom of each lane.