Dot-like focal contacts in adherent eosinophils, their redistribution into peripheral belts, and correlated effects on cell migration and protected zone formation.

We have examined the organization of F-actin and focal contacts in eosinophils and the functional consequences correlated with their predistribution. In activated eosinophils adherent to laminin, F-actin is localized in large, uniformly distributed, dot-like structures. Co-localized with the F-actin are a variety of typical components of focal contacts including: the alpha 6 and beta 1 integrins subunits (which mediate eosinophil adhesion to laminin), vinculin, talin, pp125FAK, paxillin, and tyrosine phosphorylated proteins, but not the beta 2 integrin subunit which is not involved in eosinophil adhesion to laminin.

Functional characterization of antiadhesion molecules.

Cytotactin, cytotactin binding (CTB) proteoglycan, and several other extracellular matrix (ECM) proteins and proteoglycans are described as antiadhesion molecules because they inhibit cell spreading and attachment to normally permissive ECM proteins. For cytotactin and CTB proteoglycan, this effect appears to be due to the binding of these proteins to their cell-surface receptors, which initiates a transmembrane signal that inhibits cell spreading. In contrast, the binding of fibronectin or laminin to its cell-surface receptors promotes cell spreading.

Eosinophil adhesion and maturation is modulated by laminin.

Eosinophils (Eo) participate in the inflammatory response to parasites, allergins, toxins, and epitopes recognized by autoimmune antibodies. Nonetheless, little attention has heretofore been paid to the interactions of Eo with extracellular matrix (ECM) proteins during their migration through the subendothelial basement membrane and into the surrounding tissue. Therefore, we have studied the adhesion of Eo to specific ECM proteins and the effect of this adhesion on Eo viability and maturation.

GTPase activity of bacteriophage T4 sheath protein.

We show by nuclear magnetic resonance studies that, following GTP hydrolysis during phage T4 sheath contraction, GDP remains bound to the sheath protein (gp18), whereas orthophosphate is released. gp18 in the contracted state has GTPase activity and can hydrolyse exogenous GTP; the reaction is calcium-dependent and displays high substrate specificity. The process comprises two steps: (1) displacement of GDP from gp18 by exogenous GTP, and (2) GTP hydrolysis proper.

Formation of complexes between long tail fibres and substructural elements of phage T4D.

Complexes of substructural elements of bacteriophage T4 (baseplates, baseplate-core complexes) with long tail fibres were obtained for the first time by complementation in vitro. A study of the organization of the complexes was carried out by PAGE, electron microscopy and sedimentation analysis. About 90% of baseplates and baseplate-core complexes were combined with fibres.

On the presence of guanosine phosphate in the tail of bacteriophage T4.

Treatment of gp18, a biologically active monomer of the structural protein of the bacteriophage T4 contractile sheath, with 0.6 M-HClO4 leads to the release of GDP, GMP and inorganic phosphate. Each gp18 molecule is shown to carry three atoms of phosphorus.