title: [Investigation of sarcoplasmic reticulum SH-groups].
abstract: 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.
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000032:analysis* / Q000201:enzymology; D013053:Spectrophotometry; D013438:Sulfhydryl Compounds / Q000032:analysis*
chemical_list: D013438:Sulfhydryl Compounds; D000252:Calcium-Transporting ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D008274:Magnesium; D002118:Calcium
vernacular_title: Issledovanie SH-grupp sarkopla3maticheskogo retikuluma.