Dynamics of cardiomyopathy-causing mutant of troponin measured by neutron scattering

Matsuo, Tatsuhito; Natali, F.*; Plazanet, M.*; Zaccai, G.*; Fujiwara, Satoru

Journal of the Physical Society of Japan, 82(Suppl.A), p.SA020_1 - SA020_5, 2013/01

https://doi.org/10.7566/JPSJS.82SA.SA020

Troponin is a protein that regulates the muscle contraction depending on the intracellular Ca concentration. K247R mutation of TnT is known to cause the hypertrophic cardiomyopathy. In this work, neutron scattering was used to detect possible changes in dynamics of troponin caused by mutation. Elastic incoherent neutron scattering experiments were carried out on solution samples of the wild type, and K247R mutant at the IN13 spectrometer at the Institut Laue-Langevin, at temperatures between 280 K and 292 K with an interval of 3 K. From the measured scattering data, force constants (k), which reflect the resilience of the protein, were calculated. The k values for the wild type and K247R mutant were 0.077 (0.035) N/m and 0.046 (0.026) N/m (mean(s.d.)), respectively. This suggests that the disease-causing mutant is more flexible than the wild type. The large flexibility might modulate Ca signal transmission mechanism, leading to the functional aberration.

Differences in internal dynamics of actin under different structural states detected by neutron scattering

Fujiwara, Satoru; Plazanet, M.*; Matsumoto, Fumiko; Oda, Toshiro*

Biophysical Journal, 94(12), p.4880 - 4889, 2008/06

https://doi.org/10.1529/biophysj.107.125302

Actin plays crucial roles in various aspects of cell motility. Flexibility of F-actin, a filamentous polymer formed by polymerization of the monomers (G-actin), is important for such a variety of functions. This flexibility allows F-actin to interact with various proteins, thereby expressing multiple functions. Understanding the variety of functions of actin thus requires understanding the flexibility of F-actin. As a first step towards this ultimate purpose, we carried out elastic incoherent neutron scattering (EINS) experiments on G-actin and F-actin under hydrated states. The mean square displacement (MSD) was estimated from the EINS measurements. Temperature dependence of MSD showed that two dynamical transitions occur at about 150 K and about 245 K, and that behavior of MSD is different between G-actin and F-actin, such that G-actin is "softer" than F-actin. The different behavior observed is ascribed to the differences in dynamical heterogeneity between F-actin and G-actin.

Internal dynamics of actin detected by neutron scattering

Fujiwara, Satoru; Plazanet, M.*; Matsumoto, Fumiko; Oda, Toshiro*

no journal, , 

no abstracts in English

Internal dynamics of actin detected by neutron scattering

Fujiwara, Satoru; Plazanet, M.*; Matsumoto, Fumiko; Oda, Toshiro*

no journal, , 

F-actin expresses a variety of functions related to cell motility. To understand how such multiple functions are possible, it is important to understand dynamical properties of F-actin at various levels from internal dynamics of the monomers through relative motions between the monomers to large-scale motions of F-actin. As a first step towards this ultimate purpose, we carried out elastic incoherent neutron scattering (EINS) experiments and quasi-elastic neutron scattering (QENS) experiments of F-actin and G-actin. It was shown from the EINS experiments that there are differences in the internal dynamics of F-actin and G-actin. Analysis of the QENS spectra on F-actin and G-actin showed that both in F-actin and G-actin, there are at least two populations of motions with distinct amplitudes and rates, that higher hydration ratios make these motions "faster", and that G-actin tends to have the motions with larger amplitudes and higher rates than those in F-actin.

Internal dynamics of F-actin studied by neutron scattering

Fujiwara, Satoru; Plazanet, M.*; Matsumoto, Fumiko; Oda, Toshiro*

no journal, , 

A variety of functions related to cell motility of F-actin, a filamentous polymer formed by polymerization of the monomers (G-actin), arises from flexibility of F-actin. Understanding the multi-functions of actin thus requires understanding flexibility of F-actin. Understanding flexibility of F-actin requires characterizing hierarchy of dynamics from internal dynamics of the actin-protomer to large-scale motions of F-actin. We performed elastic incoherent and quasielastic neutron scattering (EINS and QENS) experiments, to characterize dynamic properties of F-actin and G-actin. Analysis of the mean square displacements, estimated from the EINS experiments, showed that G-actin is softer than F-actin. Further characterization of the internal motions of the actin-protomers from the QENS spectra showed that these motions have distinct distributions in amplitudes and rates, and the differences in the behavior of F-actin and G-actin arise from the differences in this dynamical heterogeneity.

Actin dynamics observed by neutron inelastic scattering

Fujiwara, Satoru; Plazanet, M.*; Matsumoto, Fumiko; Endo, Hitoshi; Oda, Toshiro*

no journal, , 

Actin is one of the most abundant proteins in eukaryotic cells, and expresses a variety of functions related to cell motility. Actin monomers (G-actin) polymerize into the helical F-actin. It has been shown that the multiple functions of F-actin arise from flexibility of F-actin. For understanding flexibility of F-actin and thereby its multiple functions, it is important to understand dynamic properties of F-actin. We employed elastic incoherent and quasielastic neutron scattering, to characterize dynamic properties of F-actin and G-actin. We showed that the dynamics properties of F-actin and G-actin are different. Furthermore, neutron spin-echo experiments of F-actin and G-actin showed that the motions of F-actin and G-actin on nano-scales, described by single relaxation processes, are different. Diffusion constants obtained suggested the effects of internal motions of the actin-protomers.

Dynamics of water around F-actin in solution studied by neutron scattering

Fujiwara, Satoru; Plazanet, M.*; Oda, Toshiro*

no journal, ,