[蛙骨骼肌肌浆网片段对钙离子的被动结合]

[Passive binding of Ca2+ by fragments of the sarcoplasmic reticulum of frog skeletal muscles].

作者信息

Esyrev O V, Sarsenova Sh S, Uspanova Zh K, Kniazevskaia I B, Turmukhambetova V K

出版信息

Vopr Med Khim. 1982 Sep-Oct;28(5):51-5.

Abstract

A calcium binding characteristics of outside and inside vesicles as well as effects of K+, Mg2+, and acetylcholine cation on the calcium binding were studied in fragments of sarcoplasmic reticulum (SRF), isolated from frog femoral and abdominal muscles; high permeability of the preparations for Ca2+ was produced by incubation with I mM EDTA (pH 8-8.5) or with 5-10 microM ionophor X587A. Three types of Ca2+ binding were observed in the both SRF preparations: two of them exhibited the specific binding with high (K1) and low (K2) affinity and one type of unspecific binding with low affinity (Kunsp). The number of sites (n- nmol of Ca2+/mg of SRF protein) and dissociation constants (K microM) were the following SRF from abdominal muscle--n1 120, (K(1)15); n2 190, (K(2)135); Nunsp 650, (Kunsp 1625); SRF from femoral muscle--n(1)80, (K(1)64); n(2)265, (K(2)189); nunsp 500, (Kunsp 2240). The specific binding of Ca2+ in the SRF preparations was unaltered under physiological conditions in presence of KC1 0.1 M and MgCl2 1 mM if acetylcholine was added at concentration 10 mM, but the Ca2+ binding was completely inhibited at concentration 20 mM of acetylcholine. The unspecific Ca2+ binding was already inhibited at low concentrations of acetylcholine.

摘要

研究了从青蛙股肌和腹肌分离得到的肌浆网碎片（SRF）中外膜和内膜小泡的钙结合特性，以及K⁺、Mg²⁺和乙酰胆碱阳离子对钙结合的影响；通过与1 mM EDTA（pH 8 - 8.5）或5 - 10 microM离子载体X587A孵育，使制剂对Ca²⁺具有高通透性。在两种SRF制剂中均观察到三种类型的Ca²⁺结合：其中两种表现出高亲和力（K1）和低亲和力（K2）的特异性结合，以及一种低亲和力的非特异性结合（Kunsp）。结合位点的数量（n - 每毫克SRF蛋白结合的Ca²⁺的纳摩尔数）和解离常数（K microM）如下：来自腹肌的SRF——n1 120，（K(1)15）；n2 190，（K(2)135）；Nunsp 650，（Kunsp 1625）；来自股肌的SRF——n(1)80，（K(1)64）；n(2)265，（K(2)189）；nunsp 500，（Kunsp 2240）。在存在0.1 M KCl和1 mM MgCl2的生理条件下，如果加入浓度为10 mM的乙酰胆碱，SRF制剂中Ca²⁺的特异性结合未改变，但当乙酰胆碱浓度为20 mM时，Ca²⁺结合被完全抑制。非特异性Ca²⁺结合在低浓度的乙酰胆碱时就已被抑制。