Ischemic-induced cell injury results in rapid duration-dependent actin-depolymerizing factor (ADF)/cofilin-mediated disruption of the apical microvilli microfilament cores. Because intestinal microvillar microfilaments are bound and stabilized in the terminal web by the actin-binding protein tropomyosin, we questioned whether a protective effect of tropomyosin localization to the terminal web o...

The steady-state level and synthesis of a pair of polypeptides of Mr 33,000 and 35,000 in chicken embryo fibroblasts (CEF) transformed by Rous sarcoma virus (RSV) are significantly decreased relative to normal CEF; however, the decrease is more pronounced in the case of the Mr 35,000 polypeptide. These polypeptides have been identified as the alpha and beta subunits of CEF tropomyosin by select...

Methods for preparing troponin and tropomyosin from ethanol-extracted muscle are presented. Examination of these proteins by disc electrophoresis indicated that the troponin preparation is homogeneous. If precautions were taken to assure that the -SH groups of tropomyosin were not permitted to oxidize during preparation or electrophoresis, tropomyosin appeared to be nearly homogeneous. Traces o...

Tropomyosin inhibition of the rate of spontaneous polymerization of actin is associated with binding of tropomyosin to actin filaments. Rate constants determined by using a direct electron microscopic assay of elongation showed that alpha alpha- and alpha beta-tropomyosin have a small or no effect on the rate of elongation at either end of the filaments. The most likely explanation for the inhi...

The dynamic nature of actin polymers is modulated to facilitate a diverse range of cellular processes. These dynamic properties are determined by different isoforms of tropomyosin which are recruited to distinct subpopulations of actin polymers to differentially regulate their functional properties. This makes tropomyosin an attractive target for labelling discrete actin populations. We have as...

Muscle contraction relies on the interaction of myosin motors with F-actin, which is regulated through a translocation of tropomyosin by the troponin complex in response to Ca2+ The current model of muscle regulation holds that at relaxing (low-Ca2+) conditions tropomyosin blocks myosin binding sites on F-actin, whereas at activating (high-Ca2+) conditions tropomyosin translocation only partial...

The mechanism for the potentiation of the actin-activated ATPase of smooth muscle myosin by tropomyosin is investigated using smooth muscle actin, tropomyosin, and heavy meromyosin. In the presence of tropomyosin, an increase in Vmax occurs with no effect on KATPase and Kbinding at 20 mM ionic strength. Utilizing N-ethylmaleimide-treated subfragment-1, which forms rigor complexes with actin in ...

Tropomyosin is a highly conserved actin-binding protein that is found in most eukaryotic cells. It is critical for actin-filament stabilization and for cooperative regulation of many actin functions. Detailed structural information on tropomyosin is very important in order to understand the mechanisms of its action. Whereas structures of isolated tropomyosin fragments have been obtained at high...

The antiangiogenic activity of the multidomain plasma protein histidine-proline-rich glycoprotein (HPRG) is localized to its histidine-proline-rich (H/P) domain and has recently been shown to be mediated, at least partially, through binding to cell-surface tropomyosin in fibroblast growth factor-2-activated endothelial cells (X. Guan et al., Thromb Haemost, in press). HPRG and its H/P domain, b...

The interaction of chicken gizzard caldesmon with fragments of tropomyosin, generated by chemical, enzymatic, and mutational means, was studied to determine the caldesmon-binding site(s) on tropomyosin. Binding was examined by fluorescence spectroscopy and affinity chromatography. Removal of residues 1-141 and 228-284, respectively, from the NH2 and COOH ends of tropomyosin did not affect its b...