The Molecular Structure of the Magnesium Complex of Chicken Skeletal Troponin-C1

Satyshur, K.A.; Rao, S.T.; Pyżalska, D.; Drendel, William B.; Greaser, Marion L.; Sundaralingam, M.

doi:10.1016/b978-0-12-521040-9.50063-2

Cited by 29 publications

(57 citation statements)

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“…at the same position in calmodulin as in NTnC .2Ca, even TnC (Satyshur et al, 1988), is removed upon calcium binding, though calmodulin lacks the N-helix.…”

Section: Discussionmentioning

confidence: 99%

“…The crystal structure of turkey skeletal TnC (Herzberg & James, 1988) and of chicken skeletal TnC (Satyshur et al, 1988(Satyshur et al, , 1994) revealed a 66% a-helical protein having 2 globular domains, each containing 2 calcium-binding sites, connected by an extended a-helix. In these structures, only sites I11 and IV in the C-terminal domain are occupied by Ca2+, whereas the regulatory sites in the N-domain are in the apo state.…”

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confidence: 99%

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Quantification of the calcium‐induced secondary structural changes in the regulatory domain of troponin‐C

et al. 1994

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The backbone resonance assignments have been completed for the apo ('H and "N) and calcium-loaded ('H, IsN, and 13C) regulatory N-domain of chicken skeletal troponin-C (1-90), using multidimensional homonuclear and heteronuclear NMR spectroscopy. The chemical-shift information, along with detailed NOE analysis and 3JHNHa coupling constants, permitted the determination and quantification of the Ca2+-induced secondary structural change in the N-domain of TnC. For both structures, 5 helices and 2 short 0-strands were found, as was observed in the apo N-domain of the crystal structure of whole TnC (Herzberg 0, James MNG, 1988, JMol Biol 203:761-779). The NMR solution structure of the apo form is indistinguishable from the crystal structure, whereas some structural differences are evident when comparing the 2Ca2+ state solution structure with the apo one. The major conformational change observed is the straightening of helix-B upon Ca2+ binding. The possible importance and role of this conformational change is explored. Previous CD studies on the regulatory domain of TnC showed a significant Ca2+-induced increase in negative ellipticity, suggesting a significant increase in helical content upon Ca2+ binding. The present study shows that there is virtually no change in a-helical content associated with the transition from apo to the 2Ca2+ state of the N-domain of TnC. Therefore, the Ca2+-induced increase in ellipticity observed by CD does not relate to a change in helical content, but more likely to changes in spatial orientation of helices.Keywords: calcium; CD; NMR; regulatory domain of troponin-C; secondary structural change Troponin-C has a key role in muscle contraction of vertebrate striated muscle (skeletal and cardiac). The binding of Ca2+ to TnC induces a conformational change that affects the interaction between TnC, troponin-I (TnI), and troponin-T (TnT). This interaction blocks the inhibitory action of TnI, allowing formation of the Mg2+-activated ATPase actomyosin complex, and ultimately leads to muscle contraction. The roles and interactions of proteins in the regulatory system of striated muscle have been studied extensively (Leavis & Gergely, 1984; Ohtsuki et al.,

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“…at the same position in calmodulin as in NTnC .2Ca, even TnC (Satyshur et al, 1988), is removed upon calcium binding, though calmodulin lacks the N-helix.…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Quantification of the calcium‐induced secondary structural changes in the regulatory domain of troponin‐C

et al. 1994

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“…SANS studies of the ternary cTn further revealed the effect of phosphorylation of the two protein kinase A dependent phosphorylation sites in the cardiac-specific N-terminal extension in cTnI ($ 27-33 residues); this phosphorylation in known to result in a reduction in myofilament Ca 21 sensitivity and an increase in relaxation and cross-bridging cycle kinetics. [25][26][27] All of the high-resolution structures of sTnC and cTnC show the characteristic dumbbell shape with two globular domains separated by an extended, solvent-exposed helix of 7-8 turns [28][29][30][31][32] 41 and Heidorn and Trewhella 42 presented the first SAXS studies of rabbit sTnC that showed that the two globular domains of sTnC are on average closer together in solution than they are in the crystal structure. This interpretation was evident in the P(r) profile, which showed a peak with a shoulder in the distribution rather than the two resolved peaks indicative of two separate domains and suggested that, like calmodulin, the helix connecting the two globular EF-hand domains was flexible in solution.…”

Section: Skeletal and Cardiac Isoforms Of Troponinmentioning

confidence: 99%

“…Analysis of the contrast dependence of the R g values from the complex revealed that the centers of mass of the two components are coincident. Using a Monte Carlo modeling approach, together with the available crystal structure of 2Ca 21 Á sTnC, 29,47 Olah and Trewhella 48 generated a model for the skeletal 4Ca 21 Á sTnC-sTnI complex. In the crystal structure of 2Ca 21 Á sTnC, only the highaffinity Ca 21 binding sites at the C-terminal domain are occupied and to best-fit the scattering data, it was necessary to modify the N-terminal domain in the crystal structure to be more open, mimicking the Ca 21 bound C-terminal domain.…”

Section: Skeletal and Cardiac Isoforms Of Troponinmentioning

confidence: 99%

Invited review: Probing the structures of muscle regulatory proteins using small‐angle solution scattering

Jeffries

Trewhella

2011

Biopolymers

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Small‐angle X‐ray and neutron scattering with contrast variation have made important contributions in advancing our understanding of muscle regulatory protein structures in the context of the dynamic molecular processes governing muscle action. The contributions of the scattering investigations have depended upon the results of key crystallographic, NMR, and electron microscopy experiments that have provided detailed structural information that has aided in the interpretation of the scattering data. This review will cover the advances made using small‐angle scattering techniques, in combination with the results from these complementary techniques, in probing the structures of troponin and myosin binding protein C. A focus of the troponin work has been to understand the isoform differences between the skeletal and cardiac isoforms of this major calcium receptor in muscle. In the case of myosin binding protein C, significant data are accumulating, indicating that this protein may act to modulate the primary calcium signals from troponin, and interest in its biological role has grown because of linkages between gene mutations in the cardiac isoform and serious heart disease. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 505–516, 2011.

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“…biochem.uwo.ca. Declercq et al, 1988;Swain et al, 1989), oncomodulin (Ahmed et al, 1990), and calbindin Dgk (Szebenyi et al, 1986) each form a 2-site domain, whereas the 4 calcium-binding sites in TnC (Herzberg & James, 1988;Satyshur et al, 1988) and calmodulin (Babu et al, 1988) form 2 independent 2-site domains. An analysis of these X-ray structures reveals several common structural components (Strynadka & James, 1989).…”

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Relative stabilities of synthetic peptide homo‐ and heterodimeric troponin‐C domains

et al. 1994

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It has previously been shown that synthetic peptides corresponding to calcium-binding sites I11 (SCIII) and IV (SCIV) from troponin-C can undergo a calcium-induced dimerization to form the respective homodimers (Shaw CS, Hodges RS, Sykes BD, 1990, Science 249:280-283;Shaw CS et al., 1992a, J A m Chem SOC 114:6258-6259). In addition, an equimolar mixture of SCIII and SCIV has been shown to form preferentially the SCIII/SCIV heterodimer (Shaw CS et al., 1992a, J A m Chem SOC 114:6258-6259). The stabilities of these dimers have been investigated by using 'H-NMR and circular dichroism spectroscopies to follow temperature-and guanidine hydrochloride (GuHC1)-induced denaturations. It has been found that the most stable species, the SCIII/SCIV heterodimer (AG?' = -64.8 kJ/mol), is about 13 kJ/mol more stable than the least stable species, the SCIV homodimer, while the SCIII homodimer is of intermediate stability. This trend of free energies agrees well with the trend of AGO values derived from the products of the dissociation constants for calcium binding and peptide association determined from earlier calcium-titration studies. These observations provide evidence that calcium affinity and the association of 2-calcium binding sites are tightly linked. However, it was noted that in all cases AGO was considerably more negative than AGFZo determined from GuHCl experiments. This difference increased as the stability of the peptide complex increased, providing evidence that linear extrapolation of GuHCl data for very stable proteins may significantly underestimate the value for AGO.

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The Molecular Structure of the Magnesium Complex of Chicken Skeletal Troponin-C1

Cited by 29 publications

References 3 publications

Quantification of the calcium‐induced secondary structural changes in the regulatory domain of troponin‐C

Quantification of the calcium‐induced secondary structural changes in the regulatory domain of troponin‐C

Invited review: Probing the structures of muscle regulatory proteins using small‐angle solution scattering

Relative stabilities of synthetic peptide homo‐ and heterodimeric troponin‐C domains

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