[Investigation of sarcoplasmic reticulum SH-groups]статья
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Дата последнего поиска статьи во внешних источниках: 29 мая 2015 г.
Местоположение издательства:Road Town, United Kingdom
Первая страница:306
Последняя страница:316
Аннотация:The amount and the reaction capacity of the thiol groups in the sarcoplasmic reticulum containing up to 86% of Ca-ATPase were determined using 7-chloro-4-nitrobenzo-2-hydroxo-1,3-diazole (NBD-chloride). The total amount of SH-groups interacting with NBD-chloride is about 9 moles/10(5) g of protein as determined in the excess of NBD-chloride (750 micrometers). With respect to their sensitivity to NBD-chloride the SH-groups may be divided into two classes: slow and fast ones (5,3 and 3,5 moles/10(5) g of protein, respectively). The modification constants for the fast and slow SH-groups are 0,16 and 0,015min-1. ATP (30 micrometers) decreases the number of fast groups by 1 mole/10(5) g of protein. At higher concentrations of ATP (1–3 mM) the amount of fast SH-groups is decreased by 3 moles/10(5) g of protein, their modification rate constant being decreased 2-fold. ATP at concentration of 1 mM, decreases the rate constant for the Ca-ATPase inactivation by NBD-chloride from 0.68 down to 0,073 min-1, which coincides with the modification rate constant for fast SH-groups (0,071 min-1) under the same conditions. Ca2+ at concentration of 10(-4) M increases the amount of fast thiol groups by 1 mole/10(5) g of protein, the rate constant of their modification by NBD-chloride being increased 2-fold. A half-maximal effect was observed in the presence of 5.10(-7) M Ca2+ . Mg2+ did not affect the total amount of fast thiol groups; however, it decreased their modification rate constant.