sodium-dodecyl-sulfate and methylamine

Human placental protein 14 (PP14; also known as glycodelin and progesterone-associated endometrial protein) is an immunosuppressive protein of the lipocalin structural superfamily. Mechanisms regulating serum PP14's immunosuppressive activity remain to be elucidated. In the present study, an interaction between PP14 and a major serum protein carrier, alpha(2)-macroglobulin (alpha(2)M), was documented for the first time. Using native gel electrophoresis, we showed that PP14, as well as its alternative splice variant PP14.2, binds to both alpha(2)M and methylamine-activated (MA)-alpha(2)M. Cross-competition studies demonstrated that the variants compete for binding to alpha(2)M. PP14 bound to alpha(2)M and MA-alpha(2)M with K(d) values of 167+/-70 and 221+/-56 nM (means+/-S.D.) respectively, as determined by surface plasmon resonance. Significantly, the addition of alpha(2)M or MA-alpha(2)M to a T-cell proliferation assay strongly potentiated the inhibitory capacity of PP14. On the basis of these findings, alpha(2)M emerges as the first serum protein that can physically associate with, and thereby regulate, PP14. Moreover, this represents the first documented interaction between the protein carrier alpha(2)M and a lipocalin protein.

Topics: alpha-Macroglobulins; Binding, Competitive; Cell Division; Chromatography, Affinity; Electrophoresis, Polyacrylamide Gel; Glycodelin; Glycoproteins; Humans; Hydrogen-Ion Concentration; Immunosuppressive Agents; Kinetics; Methylamines; Plasma; Pregnancy Proteins; Protein Isoforms; Sodium Dodecyl Sulfate; Surface Plasmon Resonance; T-Lymphocytes; Time Factors

Fibrinolytic enzyme inhibitors hamper the determination of the specific fibrinolytic serine protease activity. Reportedly, chemical anti-inhibitors eliminate the influence of fibrinolytic inhibitors, but it remains unclear to what extent they change the specific activity of fibrinolytic serine proteases. We studied the influence of chemical anti-inhibitors (chloramine T, flufenamate, sodium lauryl sulfate, and methylamine) on fibrinolytic serine proteases and fibrinolytic enzyme inhibitors using the physiological substrate fibrin as plasmin substrate. Low concentrations of chloramine T (0.01 mmol/l) prevent the inhibition of plasminogen activators. Higher concentrations (1 mmol/l) reduce the inhibition of plasmin, but simultaneously quench the plasminogen activator activity. Flufenamate eliminates most fibrinolytic enzyme inhibitors, but increases the activity of plasmin (apparent recovery 140%) and plasminogen activators (apparent recovery > 200%). Sodium lauryl sulfate eliminates the major fibrinolytic enzyme inhibitors, but increases the activity of plasmin (apparent recovery > 200%) and plasminogen activator, urokinase type (apparent recovery 130%). Methylamine affects only plasmin inhibition. We conclude that chemical anti-inhibitors may invalidate the analytical specificity of methods for the determination of fibrinolytic serine protease activity.

Topics: Chloramines; Enzyme Activation; Fibrinolysin; Fibrinolysis; Fibrinolytic Agents; Flufenamic Acid; Humans; Methylamines; Plasminogen Activator Inhibitor 1; Plasminogen Activators; Serine Proteinase Inhibitors; Sodium Dodecyl Sulfate; Tissue Plasminogen Activator; Tosyl Compounds; Urokinase-Type Plasminogen Activator

In the presence of methylamine and dilute lauryl sulfate (pH 8.0), the human C3 and C4 complement proteins dimerize almost completely. Under these conditions, the related complement protein C5 does not show any tendency to form dimers. This is shown by x-ray and neutron scattering at 9 degrees C and 0.15 M ionic strength. The radii of gyration of the C3 and C4 dimers are very similar, 7.7 and 7.4 nm, and the cross-sectional radii of gyration are the same, 3.4 nm. The scattering curves of the C3 and C4 dimers as well as their Fourier transforms, the p(r)-curves, can be explained by scattering from a model consisting of an elongated elliptic cylinder with semiaxes 6.5 and 2.1 nm and length of 23 nm. This elongated elliptic cylinder model is consistent with the elliptic cylinder model of C4 (Osterberg, R., Eggertsen, G., Lundwall, A., and Sjöquist, J. (1984) Int. J. Biol. Macromol. 6, 195-198) provided that the protein molecules dimerize via their cross-sectional surfaces. Also, the model is consistent with the model of the related protein, alpha 2-macroglobulin, where the four subunits are supposed to form pairwise dimers of an elliptic cylindrical form (Osterberg, R., and Malmensten, B. (1984) Eur. J. Biochem. 143, 541-544).

Topics: Buffers; Chemical Phenomena; Chemistry, Physical; Complement C3; Complement C4; Fatty Alcohols; Humans; Macromolecular Substances; Methylamines; Molecular Weight; Neutrons; Scattering, Radiation; Sodium Dodecyl Sulfate; X-Rays