Key result
A drop in pH from 7.0 to 6.5 amplified the depression of Ca2+ binding to skeletal troponin C, increasing the midpoint free Ca2+ by 3.5-fold when complexed with TnI due to reduced TnI-TnC affinity.
Population
Fast skeletal troponin C labeled with danzylaziridine, complexed with troponin I or whole troponin complex
Comparison
Acidic pH (drop from pH 7.0 to 6.5) vs Neutral pH (7.0)
Design
Preclinical
Authors
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Indicates TnI contributes to pH sensitivity of TnC; leaves open relevance to intact muscle.
Effect estimate: 1.6-fold increase (3.5-fold in complex with TnI)
The inhibitory effect of acidic pH on Ca2+ binding to skeletal troponin C is amplified by a pH-induced decrease in the affinity of troponin I for troponin C.
El-Saleh et al. (1988) studied this question. Acidic pH (drop from 7.0 to 6.5) vs. pH 7.0 was evaluated on Midpoint for the relation between free Ca2+ and Ca2+ binding to regulatory sites on TnCDanz (1.6-fold increase (3.5-fold in complex with TnI)). A drop in pH from 7.0 to 6.5 amplified the depression of Ca2+ binding to skeletal troponin C, increasing the midpoint free Ca2+ by 3.5-fold when complexed with TnI due to reduced TnI-TnC affinity.
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