Identification of N-Terminus Peptide of Human Granulocyte/Macrophage Colony-Stimulating Factor as the Site of Nucleotide Interaction

Abstract The interaction of nucleotides with recombinant human granulocyte/macrophage colony stimulating factor (rhGM-CSF) has been investigated. Utilizing nucleotide photoaffinity probes [γ 32 P]-8N 3 ATP and [β′ 32 P]-8N 3 Ap 4 A, an analog of alarmone, the specificity of interaction was demonstrated by saturation of photoinsertion by these analogs and protection of photoinsertion by these analogs in the presence of natural nucleotide. The site of photoinsertion was tentatively determined to be Ser 9 . The photolabeled cytokine has lost most of its biological activity in a cellular proliferation assay, indicating a possible physiological role for this interaction.