A circular dichroism and biological activity study on the hybrid species formed from bovine cardiac and rabbit skeletal troponin subunits

Hincke, Maxwell T.; McCubbin, William D.; Kay, Cyril M.

doi:10.1016/0014-5793(77)80657-1

Cited by 16 publications

(4 citation statements)

References 20 publications

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“…As well, skeletal Tnl is a more effective inhibitor than cardiac Tnl in both cardiac and skeletal ATPase assays (Talbot & Hodges, 1981a; Hincke et al, 1977). In addition, cardiac TnC is less effective than skeletal TnC at releasing the inhibition induced by either cardiac or skeletal Tnl.…”

mentioning

confidence: 97%

A comparative study of the interactions of synthetic peptides of the skeletal and cardiac troponin I inhibitory region with skeletal and cardiac troponin C

1991

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The cardiac and skeletal TnI inhibitory regions have identical sequences except at position 110 which contains Pro in the skeletal sequence and Thr in the cardiac sequence. The effect of the synthetic TnI inhibitory peptides [skeletal TnI peptide (104-115), cardiac TnI peptide (137-148), and a single Gly-substituted analogue at position 110] on the secondary structure of skeletal and cardiac TnC was investigated. The biphasic increases in ellipticity and tyrosine fluorescence were analyzed to determine the Ca2+ binding constants for the high- and low-affinity Ca2+ binding sites of TnC. Importantly, the skeletal and cardiac TnI peptides altered Ca2+ binding at the low-affinity sites of TnC, but the magnitude and direction of the pCa shifts depended on whether the peptides were bound to skeletal or cardiac TnC. For example, binding of skeletal TnI peptide to skeletal TnC (monitored by CD) caused a pCa shift of +0.30 unit such that a lower Ca2+ concentration was required to fill sites I and II, while binding of this peptide to cardiac TnC caused a pCa shift of -0.35 unit such that a higher Ca2+ concentration was required to fill site II. This is the first report of the alteration at the low-affinity regulatory sites (located in the N-terminal domain) by the skeletal TnI inhibitory peptide, even though the primary peptide binding site is located in the C-terminal domain of TnC, a finding which strongly indicates that there is communication between the two halves of the TnC molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

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mentioning

confidence: 97%

A comparative study of the interactions of synthetic peptides of the skeletal and cardiac troponin I inhibitory region with skeletal and cardiac troponin C

1991

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“…The molecular mechanisms involved in the cTn thin filament being less inactive at low calcium could be via a weaker TnI-actin-Tm interaction. Biochemical studies showed that cTnI is less effective at inhibiting skeletal actomyosin ATPase activity than sTnI (44,45). TnT could also contribute through its interactions with actin-Tm or TnI and TnC (46).…”

Section: General Observationsmentioning

confidence: 99%

Differences between Cardiac and Skeletal Troponin Interaction with the Thin Filament Probed by Troponin Exchange in Skeletal Myofibrils

Yang

Yamazaki

Shen

et al. 2009

Biophysical Journal

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Troponin (Tn) is the calcium-sensing protein of the thin filament. Although cardiac troponin (cTn) and skeletal troponin (sTn) accomplish the same function, their subunit interactions within Tn and with actin-tropomyosin are different. To further characterize these differences, myofibril ATPase activity as a function of pCa and labeled Tn exchange in rigor myofibrils was used to estimate Tn dissociation rates from the nonoverlap and overlap region as a function of pCa. Measurement of ATPase activity showed that skeletal myofibrils containing >96% cTn had a higher pCa 9 ATPase activity than, but similar pCa 4 activity to, sTn-containing myofibrils. Analysis of the pCa-ATPase activity relation showed that cTn myofibrils were more calcium sensitive but less cooperative (pCa50 = 6.14, nH = 1.46) than sTn myofibrils (pCa50= 5.90, nH = 3.36). The time course of labeled Tn exchange at pCa 9 and 4 were quite different between cTn and sTn. The apparent cTn dissociation rates were approximately 2-10-fold faster than sTn under all the conditions studied. The apparent dissociation rates for cTn were 5 x 10(-3) min(-1), 150 x 10(-3) min(-1), and 260 x 10(-3) min(-1), whereas for sTn they were 0.6 x 10(-3) min(-1), 88 x 10(-3) min(-1), and 68 x 10(-3) min(-1) for the nonoverlap region at pCa 9, nonoverlap region at pCa 4, and overlap region at pCa 4, respectively. Normalization of the apparent dissociation rates gives 1:30:50 for cTn compared with 1:150:110 for sTn (nonoverlap at pCa 9:nonoverlap at pCa 4:overlap at pCa 4) suggesting that calcium has a smaller influence, whereas strong cross-bridges have a larger influence on cTn dissociation compared with sTn. The higher cTn dissociation rate in the nonoverlap region and ATPase activity at pCa 9 suggest that it gives a less off or inactive thin filament. Analysis of the intensity ratio (after a short time of exchange) as a function of pCa showed that cTn had greater calcium sensitivity but lower cooperativity than sTn. In addition, the magnitude of the change in intensity ratio going from pCa 9 to 4 was less for cTn than sTn. These data suggest that the influence of calcium on cTn exchange is less than sTn even though calcium can activate ATPase activity to a similar extent in cTn compared with sTn myofibrils. This may be explained partially by cTn being less off or inactive at pCa 9. Modeling of the intensity profiles obtained after Tn exchange at pCa 5.8 suggest that the profiles are best explained by a model that includes a long-range cross-bridge effect that grades with distance from the rigor cross-bridge for both cTn and sTn.

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“…FurtherBurtnick & Kay, 1976;Hincke et al, 1977 Fig. 4 and compared with the calculated spectrum obtained by adding the individual c.d.…”

Section: Perturbation Studies Of Troponinmentioning

confidence: 99%

“…However, current c.d. studies of troponin have emphasized the effects of Ca2+ on the subunits and the reconstituted complexes only (Murray & Kay, 1972;McCubbin et al, 1974;Mani et al, 1974Mani et al, , 1975Hincke et al, 1977). Although the observed Ca2+-induced changes in the far-u.v.…”

mentioning

confidence: 99%

Circular-dichroic studies on the conformational behaviour of troponin and tropomyosin from bovine cardiac muscle

Lin¹,

Cassim²

1978

Biochemical Journal

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Bovine cardiac troponin is similar to rabbit skeletal troponin with respect to secondary structure, amino acid composition and molecular weight of the subunits, but differs slightly with respect to biological activity and surface charges of the subunits. Previous circular-dichroic studies of the subunits and recombination of subunits have indicated significant Ca2+-induced delocalized conformational changes. Present studies of the native troponin complex are not in accord with such changes. Furthermore the formation of the troponin-tropomyosin complex in vitro results in no delocalized conformational changes, nor does it sensitize troponin to Ca2+-induced changes. It is suggested that the troponin complex cannot be dissociated into subunits without significant and irreversible conformational perturbation.

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A circular dichroism and biological activity study on the hybrid species formed from bovine cardiac and rabbit skeletal troponin subunits

Cited by 16 publications

References 20 publications

A comparative study of the interactions of synthetic peptides of the skeletal and cardiac troponin I inhibitory region with skeletal and cardiac troponin C

A comparative study of the interactions of synthetic peptides of the skeletal and cardiac troponin I inhibitory region with skeletal and cardiac troponin C

Differences between Cardiac and Skeletal Troponin Interaction with the Thin Filament Probed by Troponin Exchange in Skeletal Myofibrils

Circular-dichroic studies on the conformational behaviour of troponin and tropomyosin from bovine cardiac muscle

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