Equilibrium measurements of the rate of binding of caldesmon and myosin S1 to actin-tropomyosin from different laboratories have yielded different results and have led to different models of caldesmon function. An alternate approach to answering these questions is to study the kinetics of binding of both caldesmon and S1 to actin. We observed that caldesmon decreased the rate of binding of S1 t...

Polar residues lying between adjacent α-helical chains of coiled-coils often contribute to coiled-coil curvature and flexibility, while more typical core hydrophobic residues anneal the chains together. In tropomyosins, ranging from smooth and skeletal muscle to cytoplasmic isoforms, a highly conserved Asp at residue 137 places negative charges within the tropomyosin coiled-coil core in a posit...

Endothelial cells are actively involved in regulating the exchanges between blood and tissues. This function is tightly dependent on actin cytoskeleton dynamics and is challenged by a wide variety of stimuli, including oxidative stress. In endothelial cells, oxidative stress quickly activates the extracellular-signal-regulated kinase (ERK) MAP kinase, which results in the phosphorylation of tro...

Tropomyosins are highly conserved, coiled-coil actin binding proteins found in most eukaryotic cells. Striated and smooth muscle alpha-tropomyosins differ by the regions encoded by exons 2 and 9. Unacetylated smooth tropomyosin expressed in Escherichia coli binds actin with high affinity, whereas unacetylated striated tropomyosin requires troponin, found only in striated muscle, for strong acti...

BACKGROUND The mosquito Aedes aegypti is a potential source of important clinically relevant allergens. However, the allergenicity and cross-reactivity of most of these has not been fully described. METHODS Natural wild-type mosquito tropomyosin was purified by size exclusion and anionic-exchange chromatography from an A. aegypti extract. Further characterization was accomplished by MALDI-TOF...

OBJECTIVES We investigated the incidence and contribution of the oxidation/nitrosylation of tropomyosin and actin to the contractile impairment and cardiomyocyte injury occurring in human end-stage heart failure (HF) as compared with nonfailing donor hearts. BACKGROUND Although there is growing evidence that augmented intracellular accumulation of reactive oxygen/nitrogen species may play a k...

We have isolated a cDNA clone from a human fibroblast cDNA library that contains the entire protein-coding region of a 1.1-kilobase mRNA. This mRNA encodes a 284-amino acid tropomyosin, the primary structure of which most closely resembles smooth muscle tropomyosin. Thus, the expression of both 284-amino acid muscle-type and 247-amino acid non-muscle-type tropomyosins appears to be a normal fea...

Actin filament functional diversity is paralleled by variation in the composition of isoforms of tropomyosin in these filaments. Although the role of tropomyosin is well understood in skeletal muscle, where it regulates the actin-myosin interaction, its role in the cytoskeleton has been obscure. The intracellular sorting of tropomyosin isoforms indicated a role in spatial specialization of acti...

We discuss a theoretical model for the cooperative binding dynamics of tropomyosin to actin filaments. Tropomyosin binds to actin by occupying seven consecutive monomers. The model includes a strong attraction between attached tropomyosin molecules. We start with an empty lattice and show that the binding goes through several stages. The first stage represents fast initial binding and leaves ma...

Tropomyosin, extracted from the leg muscle of frogs that had been injected with [32P]orthophosphate, was fractionated into two components, alpha and beta, on a CM-cellulose column. Radioactivity was associated only with the alpha component. A single phosphorylation site was located at serine-283 (pentultimate at the COOH-terminal end) of the frog alpha tropomyosin. The same phosphorylated pepti...