Effect of Temperature on the Structure of Trout Troponin C

Blumenschein, Tharin M. A.; Gillis, Todd E.; Tibbits, Glen F.; Sykes, Brian D.

doi:10.1021/bi035504z

Cited by 16 publications

(12 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The authors suggest that the faster k on is caused by the mutation destabilizing the unbound or "apo" structures on the NH 2 -terminal domain, thereby making it easier for the helices to move upon Ca 2ϩ activation. These results support our interpretation of data from experiments in which the structure and Ca 2ϩ activated structural transition of cNTnC_Trout and cNTnC_Human were characterized by one-dimensional 1H and two-dimensional {1H,15N}-HSQC NMR spectroscopy (4,18,19).…”

Section: Evolution Of Troponin Csupporting

confidence: 87%

“…The residues identified as being responsible for the high (4), residue 29 is on the surface of the molecule and, therefore, exposed to solvent. The presence of a hydrophilic residue (Gln) in cTnC_Trout at residue 29 instead of a hydrophobic residue (Leu), will not, therefore, affect the stability of the core of the molecule.…”

Section: Structural Consequences Of the Nh2-terminal Sequence Differementioning

confidence: 99%

See 1 more Smart Citation

Functional and evolutionary relationships of troponin C

Gillis

Marshall

Tibbits

2007

Physiological Genomics

Self Cite

View full text Add to dashboard Cite

ated muscle contraction is initiated when, following membrane depolarization, Ca 2ϩ binds to the low-affinity Ca 2ϩ binding sites of troponin C (TnC). The Ca 2ϩ activation of this protein results in a rearrangement of the components (troponin I, troponin T, and tropomyosin) of the thin filament, resulting in increased interaction between actin and myosin and the formation of cross bridges. The functional properties of this protein are therefore critical in determining the active properties of striated muscle. To date there are 61 known TnCs that have been cloned from 41 vertebrate and invertebrate species. In vertebrate species there are also distinct fast skeletal muscle and cardiac TnC proteins. While there is relatively high conservation of the amino acid sequence of TnC homologs between species and tissue types, there is wide variation in the functional properties of these proteins. To date there has been extensive study of the structure and function of this protein and how differences in these translate into the functional properties of muscles. The purpose of this work is to integrate these studies of TnC with phylogenetic analysis to investigate how changes in the sequence and function of this protein, integrate with the evolution of striated muscle. phylogenetic analysis; protein evolution; temperature; muscle TROPONIN C (TnC), present in all striated muscle, is the Ca 2ϩ -activated trigger that initiates myocyte contraction. The binding of Ca 2ϩ to TnC initiates a cascade of conformational changes through the component proteins of the thin filament, leading to the formation of cross bridges (CBs) between actin and myosin and the generation of force by the myocyte. Therefore, the functional properties of TnC, including its ability to be activated by Ca 2ϩ , have significant regulatory influence on the contractile reaction of the myocyte. Myocyte contractility is also influenced by the strength of interaction between actin and myosin, the rate of CB cycling, and the rate of ATP hydrolysis by myosin ATPase (24). There are two muscle-specific TnC proteins found in vertebrate striated muscle. The first, skeletal TnC (sTnC), is expressed in fast skeletal muscle and the second, cardiac TnC (cTnC), is expressed in cardiac and slow skeletal muscle. A critical difference between these two paralogs is that sTnC is activated by Ca 2ϩ binding to two low-affinity sites on the NH 2 terminus of the protein (sites I and II), while cTnC is activated by Ca 2ϩ binding to a single low-affinity site (site II). Site I is nonfunctional in cTnC due to sequence manipulations that have disrupted its ability to coordinate Ca 2ϩ ion binding. cTnC and sTnC have been cloned from a variety of vertebrate species across a range of phylogenic groups. The most ancient of these is the arctic lamprey, Lampetra japonica, a member of the earliest diverged vertebrate taxon. L. japonica sTnC and cTnC are 70 and 83% identical to human sTnC and cTnC, respectively. The presence of distinct cTnC and sTnC paralogs in L. japonica suggests that these ...

show abstract

Section: Evolution Of Troponin Csupporting

confidence: 87%

Section: Structural Consequences Of the Nh2-terminal Sequence Differementioning

confidence: 99%

Functional and evolutionary relationships of troponin C

Gillis

Marshall

Tibbits

2007

Physiological Genomics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Comparison of the NMR structures of McNTnC and ScNTnC, both solved at 30°C, reveals that there are differences in the fold of the proteins. However, when ScNTnC solved at 7°C is compared with McNTnC solved at 30°C, these differences significantly decrease (1). Because 30°C and 7°C are close to the physiological temperatures of mammalian and trout hearts, respectively, these data suggest that McNTnC and ScNTnC have similar conformations at their respective physiological temperatures (1 (20).…”

Section: Camentioning

confidence: 84%

“…However, when ScNTnC solved at 7°C is compared with McNTnC solved at 30°C, these differences significantly decrease (1). Because 30°C and 7°C are close to the physiological temperatures of mammalian and trout hearts, respectively, these data suggest that McNTnC and ScNTnC have similar conformations at their respective physiological temperatures (1 (20). FHC, one of the most frequently inherited cardiac disorders, is caused by mutations in a number of the sarcomeric proteins (31).…”

Section: Camentioning

confidence: 86%

Increasing mammalian cardiomyocyte contractility with residues identified in trout troponin C

Gillis

Liang

Chung

et al. 2005

Physiological Genomics

Self Cite

View full text Add to dashboard Cite

The Ca2+ sensitivity of force generation in trout cardiac myocytes is significantly greater than that from mammalian hearts. One mechanism that we have suggested to be responsible, at least in part, for this high Ca2+ sensitivity is the isoform of cardiac troponin C (cTnC) found in trout hearts (ScTnC), which has greater than twice the Ca2+ affinity of mammalian cTnC (McTnC). Here, through a series of mutations, the residues in ScTnC responsible for its high Ca2+ affinity have been identified as being Asn2, Ile28, Gln29, and Asp30. When these residues in McTnC were mutated to the trout-equivalent amino acid, the Ca2+ affinity of the molecule, determined by monitoring the fluorescence of a Trp inserted for a Phe at residue 27, is comparable to that of ScTnC. To determine how a McTnC mutant containing Asn2, Ile28, Gln29, and Asp30 (NIQD McTnC) affects the Ca2+ sensitivity of force generation, endogenous cTnC in single, chemically skinned rabbit cardiomyocytes was replaced with either wild-type McTnC or NIQD McTnC. Our results demonstrate that the cardiomyocytes containing NIQD McTnC were approximately twice as sensitive to Ca2+, illustrating that a McTnC mutant with similar Ca2+ affinity as ScTnC can be used to sensitize mammalian cardiac myocytes to Ca2+.

show abstract

“…Since the L29Q substitution occurs naturally in trout cTnC, which possesses the second weak Ca 2+ binding site I, 24 we attempted to fit the NMR data for Ca 2+ titration of L29Q by a two-binding-site model, using K d1 for site II (determined in competitive assays) as a fixed parameter. Three curves corresponding to K d2 values of 5, 0.5, and 0.05 mM shown in Fig.…”

Section: Resultsmentioning

confidence: 99%