The search for the elusive adrenal steroidogenic "regulatory" protein.
Inhibition of protein synthesis blocks ACTH-stimulated steroidogenesis. Researchers have proposed that a "regulatory" protein functions at an intramitochondrial site to promote the translocation of cholesterol substrate from the outer to the inner membrane where the rate-limiting P-450(scc) enzyme complex is located. To date three different proteins have been put forth as a "regulatory" protein. These are structurally distinct, yet appear to perform the same in vitro function; they are widely distributed, and are normally involved in disparate activities unrelated to steroidogenesis. Thus, it is difficult to understand how a physiological role for the three proteins in ACTH-stimulated steroidogenesis might exist.
Strott
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Section on Adrenal Cell Biology, Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.