| 摘 要： | By incubating soluble F_1 of the beef heart mitochondria with radio active 7-chloro-4-nitro-2, 1, 3-benzoxadiazole (~(14)C)-NBD-C1 in the dark, a labeled F_1 with NBD/F1 molar ratio of 1: 1 (0.995: 1) wasobtained, but 98% of the ATPase activity was inhibited. The inactivated ATPase activity of the NBD-labeled F_1 may be restored by DTT, suggesting that an essential tyrosine residue of F_1 (O-NBD-F_1) maybe labeled. By exposure of O-NBD-F_1 to reflected light, the NBD label can be transferred to an aminogroup, forming an N-NBD-F_1 with 0.83 NBD label per F_1 molecule and a stable 82.5% inhibition ofthe ATPase activity even in the presence of DTT. Urea PAGE analysis clearly showed that a 63.4% ofthe total radio activity was associated with the β-subunit. In the β-fraction from N-NBD-F_1 only a 19.9-20% of the labeling was detected. It is calculated that F_1 of the beef heart mitochondria contains 3(2.63-2.64) β-subunits. The results obtained are discussed in connection with the subunit-subunit andsite-
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