Androgen binding proteins in Cochliobolus lunatus

Testosterone and 4-androstene-3,17-dione (androstenedione) binding proteins were found in the cytosol of Cochliobolus lunatus, a filamentous fungus. The maximal androgen binding occurrd by 120 min at 0°C. Androgen binding proteins were degraded by protease treatment and at high temperature. The mean K determined for testosterone binding protein (TBP) by Scatchard analysis was 4.5 nM and the maximum capacity B was 120 fmol/mg protein; for androstenedione binding protein (ABP) the K was 8 nM and B was 390 fmol/mg protein. Steroid binding specificity for TBP, in order of decreasing affinity, was the following: androstenedione, progesterone, dihydrotestosterone, 17β-estradiol and estrone. The same order was found for ABP. © 1993.