S

Mullerian Inhibitory Factor (MIF)

Precursor/Activin Form (?)

57 kDa

12.5 kDa

Mature MIF 12.5 kDa

2. Inhibin

The regulation of secretion of FSH from the adenohypophysis is only partly dependent on gonadal steroids; in addition, the protein hormone inhibin acts principally at the level of the pituitary to diminish the secretion of FSH. Inhibin is a hormone secreted in males by the Sertoli cells and in females by the ovarian follicles.

Inhibin is a heterodimeric protein; it has a common a-subunit and one of two /3-subunits. Thus, there are two isoforms of inhibins, either inhibin A (a/3A) or inhibin B (a/3B) (see Figure 12-6). The /3-subunit is 18 kDa and the a-subunit is 14 kDa. Structurally the inhibins belong to the transforming growth factor (TGF-)3) multigene family (see Chapter 19). The a-and /3-subunits are cross-linked by one or more disulfide bridges. As yet, it is not known whether the detailed structures of male- and female-derived inhibins are identical.

The structure of the inhibins is also related to that of another peptide hormone, the activins (see the following). Figure 12-6 compares the structures of inhibins and activins.

Both subunits of mature inhibin are derived from precursor prohormone species. Thus, the a-subunit's primary transcript contains 364 amino acids, while the jS-subunit's primary transcript contains 424 amino 140 kDa acids. Both the mature a- and /3-subunits lie at the extreme carboxyl end of their respective prohormone species. Each mature subunit is preceded by either two a-subunit or five /8-subunit arginines, which constitute the cleavage sites for proteolytic release of the mature subunits. It is known that the a- and /3-subunits of biologically active inhibin are linked by disulfide

Cure Tennis Elbow Without Surgery

Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

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