Unequal S–S bond lengths in a symmetrically-substituted thiathiophthen

Johnson, Paul L.; Paul, Iain C.

doi:10.1039/c29690001014

Cited by 59 publications

(63 citation statements)

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“…It therefore appears possible that calcium removal from the regulatory sites could be faster than the conformational change. According to [9] the conformational change following the removal of magnesium from the high affinity sites is slightly faster than that following the removal of calcium, which indicates that the TnC(Ca2) protein conformation is more structured than that of TnC(Mg,), in agreement with the protein NMR study in [8]. However, our data indicate the off-rate of the Mg2+ to be 3 orders of magnitude faster than the conformational change.…”

Section: Discussionsupporting

confidence: 88%

“…We will however assume that they.were performed at ambient temperature (23-25°C) tein were too fast to be measured. In [9] it was concluded that the observed structural change (step 4) is the same as the calcium off-rate whereas for step 2 the conformational change is slower than the removal of Ca'+. Under the experimental conditions we have used, the only calcium exchange that can be observed is that involving the regulatory sites.…”

Section: Discussionmentioning

confidence: 99%

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A ⁴³Ca NMR and ²⁵Mg NMR study of rabbit skeletal muscle troponin C

et al. 1981

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

A ⁴³Ca NMR and ²⁵Mg NMR study of rabbit skeletal muscle troponin C

et al. 1981

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“…The results also suggest that cTnT stabilizes the C-terminal Ca 2ϩ off rates for sites III and IV of cTnC by nearly an order of magnitude above what cTnI alone does. The functional significance of this is unclear as the Ca 2ϩ exchange and the structural changes involved in Ca 2ϩ exchange at the Ca 2ϩ /Mg 2ϩ sites are too slow to be involved directly in the regulation of muscle contraction (23). The rates from the N-terminal cTnC Ca 2ϩ -binding site II and the Cterminal sites were separated enough in time so that there was minimal interference between them.…”

Section: ϫ015) Than Intact Fibers Similar To What Has Been Reported mentioning

confidence: 97%

Cardiac Troponin T Isoforms Affect the Ca2+ Sensitivity of Force Development in the Presence of Slow Skeletal Troponin I

Gomes¹,

Venkatraman

Davis

et al. 2004

Journal of Biological Chemistry

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In this study we investigated the physiological role of the cardiac troponin T (cTnT) isoforms in the presence of human slow skeletal troponin I (ssTnI). ssTnI is the main troponin I isoform in the fetal human heart. In reconstituted fibers containing the cTnT isoforms in the presence of ssTnI, cTnT1-containing fibers showed increased Ca 2؉ sensitivity of force development compared with cTnT3-and cTnT4-containing fibers. The maximal force in reconstituted skinned fibers was significantly greater for the cTnT1 (predominant fetal cTnT isoform) when compared with cTnT3 (adult TnT isoform) in the presence of ssTnI. Troponin (Tn) complexes containing ssTnI and reconstituted with cTnT isoforms all yielded different maximal actomyosin ATPase activities. Tn complexes containing cTnT1 and cTnT4 (both fetal isoforms) had a reduced ability to inhibit actomyosin ATPase activity when compared with cTnT3 (adult isoform) in the presence of ssTnI. The rate at which Ca 2؉ was released from site II of cTnC in the cTnI⅐cTnC complex (122/s) was 12.5-fold faster than for the ssTnI⅐cTnC complex (9.8/s). Addition of cTnT3 to the cTnI⅐cTnC complex resulted in a 3.6-fold decrease in the Ca 2؉ dissociation rate from site II of cTnC. Addition of cTnT3 to the ssTnI⅐cTnC complex resulted in a 1.9-fold increase in the Ca 2؉ dissociation rate from site II of cTnC. The rate at which Ca 2؉ dissociated from site II of cTnC in Tn complexes also depended on the cTnT isoform present. However, the TnI isoforms had greater effects on the Ca 2؉ dissociation rate of site II than the cTnT isoforms. These results suggest that the different N-terminal TnT isoforms would produce distinct functional properties in the presence of ssTnI when compared with cTnI and that each isoform would have a specific physiological role in cardiac muscle.

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“…Also there is good evidence that, in the absence of calcium, troponin (throu~ its subunit troponin I which binds to actin) holds tropomyosin at the periphery. Calcium saturation of troponin C initiates a series of conformational changes [6] that result in the dissociation of troponin I from actin [7] and allow tropomyosin to move to its natural binding sites at or near the groove. ~thou~ movement of tropomyos~ is well established it is not clear that tropomyosin and myosin actually compete for the same binding sites on the actin filament.…”

Section: Introductionmentioning

confidence: 99%