BINDING OF HUMAN PLACENTAL RIBONUCLEASE INHIBITOR TO EXTRACELLULAR-MATRIX MOLECULES

The ribonuclease inhibitor from human placenta (HPRI) is a protein tha t inhibits pancreatic type ribonucleases (RNases) and is widely utiliz ed in the field of molecular biology. We investigated the binding abil ity of biotinylated HPRI to the extracellular matrix (ECM) molecules b y the use of an enzyme-conjugated streptavidin system. Biotin-HPRI bou nd to RNase A and to a number of ECM molecules such as collagens, lami nin and fibronectin, whereas only weak binding activity was observed t o some serum proteins such as albumin, transferrin, IgG, vitronectin a nd fibrinogen under the same experimental condition. The binding of bi otin-HPRI to the ECM molecules was not inhibited by the addition of RN ase A, suggesting that the binding mechanism for ECM molecules is diff erent from that for RNase A.