{'fraction_non_alphanumeric': 0.025769506084466716, 'fraction_numerical': 0.010021474588403722, 'mean_word_length': 5.5327102803738315, '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}}
Transforming growth factor beta receptor signaling and endocytosis are linked through a COOH terminal activation motif in the type I receptor.

Transforming growth factor beta (TGF-beta) coordinates a number of biological events important in normal and pathophysiological growth. In this study, deletion and substitution mutations were used to identify receptor motifs modulating TGF-beta receptor activity. Initial experiments indicated that a COOH-terminal sequence between amino acids 482-491 in the kinase domain of the type I receptor was required for ligand-induced receptor signaling and down-regulation. These 10 amino acids are highly conserved in mammalian, Xenopus, and Drosophila type I receptors. Although mutation or deletion of the region (referred to as the NANDOR BOX, for nonactivating non-down-regulating) abolishes TGF-beta-dependent mitogenesis, transcriptional activity, type I receptor phosphorylation, and down-regulation in mesenchymal cultures, adjacent mutations also within the kinase domain are without effect. Moreover, a kinase-defective type I receptor can functionally complement a mutant BOX expressing type I receptor, documenting that when the BOX mutant is activated, it has kinase activity. These results indicate that the sequence between 482 and 491 in the type I receptor provides a critical function regulating activation of the TGF-beta receptor complex.