Faculty Bibliography

Supernatant fractions from rat pancreas bind approximately 300 fmol of [3H]estradiol per mg of protein when incubated with 5 nM [3H]estradiol for 1 hr at room temperature. Passage through gel filtration columns reduces binding in the eluate to approximately 1% of its initial activity. Extracts of the supernatant contain a factor that reactivates binding in gel filtrates. Addition of accessory factor to fractional eluates gives one sharp peak of activity. Since fractions that cannot be reactivated contain as much or more protein as fractions that can be reactivated, it is concluded that interaction of accessory factor and [3H]estradiol-binding protein is specific. Peptides such as antipain [(1-carboxy-2-phenylethyl)carbamoyl-L-arginyl-L-valyl-L-argininal] and, especially, N-benzoyl-L-phenylalanyl-L-valyl-L-arginine-p-nitroanilide also enhanced binding of [3H]estradiol. Accessory factor is water soluble, dialyzable, and heat stable. Although as currently purified, it contains several substances, the data suggest that at least one component of accessory factor is an oligopeptide

In parallel sets of experiments, cytosol fractions from rat pancreas and uterus were incubated with 2 nM 3H-estradiol in the presence or absence of nuclei from pancreas and liver. After incubation for 1 hr at room temperature, the nuclei were removed by centrifugation and specific binding determined in the cytosol fractions as well as in the separated nuclei. The protein that binds 3H-estradiol in uterine extracts translocated the hormone to nuclei of pancreas and liver while the one in pancreas was devoid of this activity. It is presumed, therefore, that modification of transcription is not a primary action of the steroid-bound complex in pancreas