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Biomedical subjects

D J Fishkind

Publications and source records attributed to D J Fishkind.

22 records · Page 2Linked to original sources
PubMed1985

Actin assembly and filament cross-linking in the presence of TW 260/240, the tissue-specific spectrin of the chicken intestinal brush border.

TW 260/240 is a tissue-specific spectrin found in the terminal web region of the chicken intestinal brush border. We have examined the effects of TW 260/240 on assembly rates and critical concentrations (Co's) for monomer addition at the barbed and pointed ends of the actin filament. For these studies, acrosomal processes (AP) from Limulus sperm were used as nuclei for actin assembly. Under conditions which favor the interaction of TW 260/240 for actin (20-75 mM KCl, 2 mM Mg++) no effect on either elongation rates or Co's at either end of the actin filament was observed in the presence of this spectrinlike protein. The Limulus AP nucleation assay also allowed visualization of the kinetics of filament binding and cross-linking by TW 260/240. Ultrastructural analysis of TW 260/240 binding to actin filaments at their growing ends indicates that TW 260/240 tetramers bind laterally to the filament. Finally, evidence is presented that indicates that filaments cross-linked by TW 260/240 are stabilized against shear-dependent breakage.

Acrosome↗
PubMed1983

Direct measurement of critical concentrations and assembly rate constants at the two ends of an actin filament.

Actin filament bundles isolated from Limulus sperm were used for quantitative electron microscope studies of F-actin assembly. The assembly rate constants were calculated. In addition, the critical concentrations (Cos) for both filament ends were directly determined. In 75 mM KCl and 1-5 mM Mg++, the Cos were 0.1 microM and 0.5 microM for the barbed and pointed ends, respectively. Substitution of Ca++ (20-200 microM) for Mg++ resulted in Cos of 0.4 microM for both filament ends. Consistent with these findings, filament growth occurred only from the barbed ends of Limulus bundles "seeded" into F-actin solutions in KCl and Mg++. Finally, filaments originally grown from the pointed filament ends of Limulus bundles were gradually lost as the actin solution reached steady state. These results demonstrate that actin filaments can "treadmill" under physiological conditions, albeit at very slow rates.

Actins↗