Guillot D, Vard C, Reboud JP. Photoaffinity labeling of elongation factor-2 with 8-azido derivatives of GTP and ATP.
EUROPEAN JOURNAL OF BIOCHEMISTRY 1996;
236:149-54. [PMID:
8617259 DOI:
10.1111/j.1432-1033.1996.00149.x]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Elongation factor 2 (eEF-2) can interact not only with guanylic nucleotides but also with adenylic ones, as was shown by intrinsic fluorescence quenching studies [Sontag, B., Reboud, A.M., Divita, G., Di Pietro, A., Guillot, D. & Reboud, J.P. (1993) Biochemistry 32, 1976-1980]. Here we studied sites of these interactions by using photoactivable 8-azido-[gamma-32P]GTP and 8-azido-[gamma-32P]ATP. Photoincorporation of the radioactive GTP derivative into eEF-2 was prevented by the previous addition of GTP and GDP. The addition of adenylic nucleotides (ATP, ADP) and some adenylic derivatives [NAD+, NADH,poly(A)] decreased the photoincorporation by only 40% at most. However, photoincorporation of the radioactive ATP derivative was prevented by the previous addition not only of adenylic compounds [ATP, ADP, NAD+, NADH, poly(A)] but also of GTP and GDP. Photoincorporation of radioactive nucleotide derivatives was not decreased by the addition of other nucleotidic compounds [UTP, poly(U), ITP, NADP+, NADPH]. ATP and GTP acted as non-competitive inhibitors of the photoincorporation of 8-azido-[gamma-32P]GTP and 8-azido-[gamma-32P]ATP, respectively. eEF-2 photolabeled with these radioactive nucleotide derivatives was submitted to trypsin digestion under different conditions and the labeled peptidic fragments identified after HPLC purification and gel electrophoresis by N-terminal sequencing. An octapeptide, Y264FDPANGK271, was the only peptide photolabeled with 8-azido-[gamma-32P]GTP whereas a N-terminal fragment of about 7 kDa was the only one photolabeled with 8-azido-[gamma-32P]ATP. The different results support the hypothesis that guanylic and adenylic nucleotides do not interact with the same site of eEF-2.
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