Isolation and partial molecular characterization of pituitary fibroblast growth factor.

Abstract

Fibroblast growth factor (FGF) was purified to homogeneity from bovine pituitaries by 2 methods. Starting material for both methods was an FGF preparation partially purified as described by Gospodarowicz. Purification procedure I involved cation-exchange and reversed-phase HPLC [high performance liquid chromatography], while procedure II employed gel filtration and ion-exchange chromatography. Isolation was monitored by testing column fractions for their capacity to stimulate the proliferation of vascular endothelial cells in vitro. The growth factor has an approximate MW of 16,000. Its amino-terminal sequence was determined as Pro-Ala-Leu-Pro-Glu-Asp-Gly-Gly-Ser-Gly-Ala-Phe-Pro-Pro-Gly. Sequence and amino acid composition indicate that the structure of pituitary FGF is different from that of other known growth factors. Pituitary FGF, as isolated under nonacidic conditions (procedure II), has high potency and intrinsic activity to stimulate adult bovine aortic endothelial cells (half-maximal proliferation at 2 pM). Acidic conditions, as in procedure I, lead to about 90% loss of potency while the intrinsic activity remains intact (identical maximal stimulation values). By all other criteria (MW, amino acid composition, amino-terminal sequence), the 2 preparations are indistinguishable. Antibodies were raised in rabbits against a synthetic peptide representing the first 9 residues of the amino-terminal sequence of the pituitary FGF. The polyclonal antibodies recognize the synthetic peptide and the purified growth factor on an equimolar basis and are capable of inhibiting mitogenic activity in vitro. This report describes a partial chemical characterization of a pituitary FGF and demonstrates rigorously that the characterized protein possesses the mitogenic activity commonly referred to as basic pituitary FGF.