{'fraction_non_alphanumeric': 0.04426229508196721, 'fraction_numerical': 0.018579234972677595, 'mean_word_length': 4.794303797468355, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Mapping of human granulocyte-macrophage-colony-stimulating-factor domains interacting with the human granulocyte-macrophage-colony-stimulating-factor-receptor alpha-subunit.

The high-affinity granulocyte-macrophage-colony-stimulating-factor (GM-CSF) receptor (R) is composed of at least two subunits, termed alpha and beta. The alpha subunit is crucial for initiating ligand/receptor interaction and for ligand specificity. The experiments reported in this study sought to identify the domains of human (h)GM-CSF which are responsible for interaction with hGM-CSFR alpha. Anti-(human-GM-CSF) mAb were used as competitors in a 125I-GM-CSF receptor-binding assay on cells expressing the recombinant hGM-CSFR alpha chain. Inhibition of 125I-GM-CSF binding to the GM-CSFR alpha chain was demonstrated by mAb which mapped to the middle third of the third alpha helix (amino acids 78-83), the distal two-thirds of the third alpha helix and the initial 7 residues of the loop between the third and fourth helix (amino acids 78-94), and the extreme carboxy terminus. No inhibition of binding occured with an antibody whose domain begins in the first beta-pleated sheet (amino acids, 39-43), continues through the second helix (amino acids 55-64) and into the proximal third of the third helix (to amino acid 77). mAb which mapped to the distal half of the fourth helix and the carboxy-terminal tail (amino acids 110-127) increased the binding of 125I-GM-CSF to GM-CSFR alpha. Due to the known discontinous epitopes the possibility that the distal portion of the fourth helix contributes to binding cannot be eliminated. However, the domains of hGM-CSF most clearly involved in binding to the hGM-CSFR alpha are the distal two-thirds of the third alpha helix, the immediate downstream residues and the extreme carboxy terminus of hGM-CSF.