Eager K R, Dulhunty A F
Muscle Research Group, John Curtin School of Medical Research, Canberra, Australia.
J Membr Biol. 1998 May 1;163(1):9-18. doi: 10.1007/s002329900365.
The reactive disulfide 4,4'-dithiodipyridine (4,4' DTDP) was added to single cardiac ryanodine receptors (RyRs) in lipid bilayers. The activity of native RyRs, with cytoplasmic (cis) [Ca2+] of 10(-7) M (in the absence of Mg2+ and ATP), increased within approximately 1 min of addition of 1 mM 4,4'-DTDP, and then irreversibly ceased 5 to 6 min after the addition. Channels, inhibited by either 1 mM cis Mg2+ (10(-7) M cis Ca2+) or by 10 mM cis Mg2+ (10(-3) M cis Ca2+), or activated by 4 mM ATP (10(-7) M cis Ca2+), also responded to 1 mM cis 4,4'-DTDP with activation and then loss of activity. Po and mean open time (T(o)) of the maximally activated channels were lower in the presence of Mg2+ than in its absence, and the number of openings within the long time constant components of the open time distribution was reduced. In contrast to the reduced activation by 1 mM 4,4'-DTDP in channels inhibited by Mg2+, and the previously reported enhanced activation by 4,4'-DTDP in channels activated by Ca2+ or caffeine (Eager et al., 1997), the activation produced by 1 mM cis 4,4'-DTDP was the same in the presence and absence of ATP. These results suggest that there is a physical interaction between the ATP binding domain of the cardiac RyR and the SH groups whose oxidation leads to channel activation.
将反应性二硫化合物4,4'-二硫代二吡啶（4,4'-DTDP）添加到脂质双分子层中的单个心肌兰尼碱受体（RyRs）中。在细胞质（顺式）[Ca2+]为10^(-7) M（不存在Mg2+和ATP）的情况下，天然RyRs的活性在添加1 mM 4,4'-DTDP后约1分钟内增加，然后在添加后5至6分钟不可逆地停止。被1 mM顺式Mg2+（10^(-7) M顺式Ca2+）或10 mM顺式Mg2+（10^(-3) M顺式Ca2+）抑制，或被4 mM ATP（10^(-7) M顺式Ca2+）激活的通道，也对1 mM顺式4,4'-DTDP有反应，先激活然后失去活性。在存在Mg2+的情况下，最大激活通道的Po和平均开放时间（T(o)）比不存在时低，并且开放时间分布的长时间常数成分内的开放次数减少。与Mg2+抑制的通道中1 mM 4,4'-DTDP激活减少以及先前报道的Ca2+或咖啡因激活的通道中4,4'-DTDP激活增强相反（Eager等人，1997），1 mM顺式4,4'-DTDP在存在和不存在ATP的情况下产生的激活是相同的。这些结果表明，心肌RyR的ATP结合结构域与SH基团之间存在物理相互作用，其氧化导致通道激活。
