Effect of temperature on relaxation rate and Ca2+, Mg2+ dissociation rates from parvalbumin of frog muscle fibres.

Abstract

SUMMARY1. Influence of temperature on relaxation rate as a function of isometric tetanus duration and on Ca2" and Mg2" dissociation rates from purified parvalbumin (PA) was examined to test the hypothesis that PA promotes relaxation in frog skeletal muscle. Single fibres and PA IVB from Rana temporaria skeletal muscle were utilized.2. The magnitude of slowing of relaxation rate with increasing tetanus duration, relative to the final, steady value of relaxation rate, is 3-fold greater at 0 than at 10 OC.3. In the 0-10°C range, the Qlo for relaxation rate increases from 2-3 to 3-7 with increasing tetanus duration.

Resurrecting prehistoric parvalbumins to explore the evolution of thermal compensation in extant Antarctic fish parvalbumins

“…This analysis yields two k off values -a fast k off and a slow k off . The fast k off rates were used for data analyses and interpretation as these values correspond to previously published Ca 2+ dissociation rate constants for other PV isoforms (Hou et al, 1992;Johnson et al, 1999;Lee et al, 2000). The second, slower rate constants are an order of magnitude slower than previously reported values.…”

“…In addition to the steady-state Ca 2+ K d data, we determined the unidirectional rate constants of Ca 2+ binding and dissociation. These two rate constants define the interaction of Ca 2+ with PV and it has been shown that these parameters can directly affect muscle function (Hou et al, 1991;Hou et al, 1992). The equilibrium Ca 2+ -binding constant K d is determined by the ratio of off-rate over on-rate (K d k off /k on ).…”

“…Off-rates for Ca 2+ were measured using terbium fluorescence as a reporter ligand based on established methods (Hou et al, 1991;Hou et al, 1992). PV has a higher affinity for terbium and the off-rate of Ca 2+ can be measured as it is replaced by terbium and terbium fluorescence increases.…”

Trading force for speed: Why superfast crossbridge kinetics leads to superlow forces

“…The rate constant for the average decay in force was measured during the initial slow phase of relaxation (i.e., when force falls from 95% to 80%, as in ref. 16), when sarcomeres are generally isometric. It should be noted that during the fast relaxation phase (i.e., when force falls from 80% to 5%), the faster fall in force is likely because of large sarcomere rearrangements (17), which cause sarcomere shortening and an increase in the crossbridge detachment rate constant above the isometric value.…”

Designing Heart Performance by Gene Transfer

“…Parv is expressed in several tissues including fast skeletal muscle but is not normally found in the mammalian heart (199). In fast skeletal muscle, Parv is thought to act as a delayed Ca 2ϩ buffer that hastens relaxation in a dose-dependent manner (352,374).…”