Is the mitochondrial Ca2+ uniporter a voltage‐modulated transport pathway?

FEBS Letters

Szászi, Katalin¹  Ligeti, Erzsébet¹  Fonyó, Attila¹  Káldi, Krisztina¹  Kapùs, András¹ 

[1]Department of Physiology, Semmelweis University of Medicine, P.O. Box 259, H-1444 Budapest 8, Hungary

关键词: Matrix [Ca2+];    Uniporter;    Membrane potential;    [Ca2+]m;    free matrix [Ca2+];    [Ca2+]o;    external free [Ca2+];    ΔΨ;    mitochondrial membrane potential;    TPP+;    tetraphenyl phosphonium ion;    CCCP;    carbonyl cyanide p-trifluoromethoxyphenylhydrazone;   

DOI  :  10.1016/0014-5793(91)80444-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The influence of membrane potential (Δψ) on Ca²⁺ transport through the Ca²⁺ uniporter (UP) was investigated in fura-2-loaded rat heart mitochondria at physiologically relevant-submicromolar-external [Ca²⁺]. In the absence of Δψ the UP could not mediate Ca²⁺ uptake even when an 8-fold external (∼500 nM) to internal (∼60 nM) [Ca²⁺] gradient was present and charge compensation was provided by acetate and the protonophore, CCCP. A small (∼−120 mV) and transient Δψ (generated by valinomycin) resulted in a rise in matrix [Ca²⁺] only when external [Ca²⁺] exceeded 150 nM. At physiologically high (∼−180 mV) and stable Δψ this threshold value for Ca²⁺ uptake dropped to 15 nM. The results indicate that (1) at physiological [Ca²⁺]_m Δψ in addition to being a component of Δμ_Ca²⁺ seems to be necessary for providing a transport-competent conformation for the UP; and (2) below a threshold [Ca²⁺]_m the UP cannot operate even in the presence of a high electric driving force.

【 授权许可】

Unknown