Photolabeling of the phosphate binding site of mitochondrial F1-ATPase by [32P]azidonitrophenyl phosphate. Identification of the photolabeled amino acid residues

Abstract
[32P]Azidonitrophenyl phosphate ([32P]ANPP) is a photoactivatable analogue of Pi. It competes efficiently with Pi for binding to the F1 sector of beef heart mitochondrial ATPase and photolables the Pi binding site located in the .beta. subunit of F1 [Lauquin, G. J. M., Pougeois, R., and Vignais, P. V. (1980) Biochemistry 19, 4620-4626]. By cleavage of the photolabeled .beta. subunit of F1 with cyanogen bromide, trypsin, and chymotrypsin, bound [32P]ANPP was localized in a fragment spanning Thr 299-Phe 326. By Edman degradation of the radiolabeled tryptic peptide spanning Ile 296-Arg 337, [32P]ANPP was found to be attached covalently by its photoreactive group to Ile 304, Gln 308, and Tyr 311. These results are discussed in terms of a model in which the phosphate group of [32P]ANPP interacts with a glycine-rich sequence of the .beta. subunit, spannig Gly 156-Lys 162, which is spatially close to the photolabeled Ile 304-Tyr 311 segment of the same subunit.

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