In vitro inhibition of the actions of basic FGF by a novel 16 amino acid peptide

We have examined the temperature-dependent effects of several organic compounds on the activity of the purified Ca²⁺-ATPase of erythrocytes. The monomeric enzyme was activated either by interaction with calmodulin or by oligomerization in the absence of calmodulin. Of the four homologous solute series studied including polyols, alkanols, aprotic solvents, and N-methyl derivatives of formamide and acetamide only polyols stabilized the enzyme over a broad range of concentration and temperature. Similarity of Ca²⁺-ATPase activity patterns at 25 and 37°C and in the presence of glycerol is in agreement with indirect, stabilizing interactions. Glycerol also protected the Ca²⁺-ATPase from thermal denaturation at 45°C. Within each homologous series, inhibitory effects increased with increasing solute concentration and with increasing structural similarity to detergents, indicating that direct destabilizing interactions are responsible for the observed inhibition. These were comparable to the destabilizing effect of urea. Oligomers were more resistant to all inhibitory solutes as compared to calmodulin-activated monomers suggesting that the nonpolar patches of the oligomerized enzyme are less accessible to solutes.