α-Tropomyosin with a D175N or E180G Mutation in Only One Chain Differs from Tropomyosin with Mutations in Both Chains
نویسندگان
چکیده
α-Tropomyosin (Tm) carrying hypertrophic cardiomyopathy mutation D175N or E180G was expressed in Escherichia coli. We have assembled dimers of two polypeptide chains in vitro that carry one (αα*) or two (α*α*) copies of the mutation. We found that the presence of the mutation has little effect on dimer assembly, thereby predicting that individuals heterozygous for the Tm mutations are likely to express both αα* and α*α* Tm. Depending on the expression level, the heterodimer may be the predominant form in individuals carrying the mutation. Thus, it is important to define differences in the properties of Tm molecules carrying one or two copies of the mutation. We examined the Tm homo- and heterodimer properties: actin affinity, thermal stability, calcium regulation of myosin subfragment 1 binding, and calcium regulation of myofibril force. We report that the properties of the heterodimer may be similar to those of the wild-type homodimer (actin affinity, thermal stability, D175N αα*), similar to those of the mutant homodimer (calcium sensitivity, D175N αα*), intermediate between the two (actin affinity, E180G αα*), or different from both (thermal stability, E180G αα*). Thus, the properties of the homodimer are not a completely reliable guide to the properties of the heterodimer.
منابع مشابه
Facilitated Cross-Bridge Interactions with Thin Filaments by Familial Hypertrophic Cardiomyopathy Mutations in α-Tropomyosin
Familial hypertrophic cardiomyopathy (FHC) is a disease of cardiac sarcomeres. To identify molecular mechanisms underlying FHC pathology, functional and structural differences in three FHC-related mutations in recombinant α-Tm (V95A, D175N, and E180G) were characterized using both conventional and modified in vitro motility assays and circular dichroism spectroscopy. Mutant Tm's exhibited reduc...
متن کاملPredicting Effects of Tropomyosin Mutations on Cardiac Muscle Contraction through Myofilament Modeling
Point mutations to the human gene TPM1 have been implicated in the development of both hypertrophic and dilated cardiomyopathies. Such observations have led to studies investigating the link between single residue changes and the biophysical behavior of the tropomyosin molecule. However, the degree to which these molecular perturbations explain the performance of intact sarcomeres containing mu...
متن کاملCardiac dysfunction in hypertrophic cardiomyopathy mutant tropomyosin mice is transgene-dependent, hypertrophy-independent, and improved by beta-blockade.
Familial hypertrophic cardiomyopathy (FHC) has been linked to mutations in proteins of the cardiac contractile apparatus, including alpha-tropomyosin (Tm). Mice expressing alphaTm in the heart were developed to determine the effects of FHC mutant Tm on cardiac structure and function from single cardiac myocytes to whole organ function in vivo. Expression of E180G mutant Tm did not produce cardi...
متن کاملParvalbumin corrects slowed relaxation in adult cardiac myocytes expressing hypertrophic cardiomyopathy-linked alpha-tropomyosin mutations.
Hypertrophic cardiomyopathy mutations A63V and E180G in alpha-tropomyosin (alpha-Tm) have been shown to cause slow cardiac muscle relaxation. In this study, we used two complementary genetic strategies, gene transfer in isolated rat myocytes and transgenesis in mice, to ascertain whether parvalbumin (Parv), a myoplasmic calcium buffer, could correct the diastolic dysfunction caused by these mut...
متن کاملCalcium, contractions, and tropomyosin Focus on "divergent abnormal muscle relaxation by hypertrophic cardiomyopathy and nemaline myopathy mutant tropomyosins".
IN SKELETAL AND CARDIAC MUSCLE, tropomyosin in association with troponin plays an essential role in Ca2 regulation of the thin filament interaction with myosin that is responsible for contraction. Tropomyosin is an elongated coiled-coil -helical dimer with 284 amino acids per peptide chain (9). Three genes code for tropomyosin in striated muscle: TPM1 for -tropomyosin; TPM2 for -tropomyosin; an...
متن کامل