A method has been devised for the partial purification of luteinizing hormone-releasing factor (LHRF) from extracts of ovine median-eminence tissue. Acid extracts are boiled for 20 min, dialyzed against water for 12 hr, and the dialysate lyophilized. The lyophilized residue is dissolved in a small volume of 5 x 10–3 m ammonium acetate, pH 4.6, and chromatographed on carboxymethylcellulose with an ammonium acetate gradient to 1.0 m, pH 4.6. Several acidic peptides pass through the column rapidly; a peptide with LHRF activity appears in the effluent at about 0.4 m ammonium acetate. The ability of various fractions to induce ovulation on intrapituitary infusion into "atropine-pentobarbital-blocked" proestrous rats was used as the biological test for the release of LH. It was found that, following the infusion of the LHRF-containing fraction, 42 of 54 animals ovulated, while no ovulation was observed in 64 animals treated with any of the other fractions. The LHRF material is probably a small polypeptide which is dialyzable, heat stable, has little absorbancy at either 260 or 280 mµ, and does not give a positive reaction with ninhydrin after paper chromatography in the solvent system used. Evidence is presented that the partially purified LHRF is devoid of LH contamination.
Interaction of replication protein A with two acidic peptides from human Bloom syndrome protein
