title: Nuclear magnetic resonance structure of the cytoplasmic tail of heparin binding EGF-like growth factor (proHB-EGF-CT) complexed with the ubiquitin homology domain of Bcl-2-associated athanogene 1 from Mus musculus (mBAG-1-UBH).
abstract: The membrane form of heparin binding EGF-like growth factor (proHB-EGF) yields secreted HB-EGF and a membrane-anchored cytoplasmic tail (proHB-EGF-CT), which may be targeted to the nuclear membrane after a shedding stimulus. Bcl-2-associated athanogene 1 (BAG-1) accumulates in the nuclei and inhibits apoptosis in adenoma-derived cell lines. The maintenance of high levels of nuclear BAG-1 enhances cell survival. However, the ubiquitin homology domain of BAG-1 from Mus musculus (mBAG-1-UBH) is proposed to interact with proHB-EGF-CT, and this interaction may enhance the cytoprotection against the apoptosis inducer. The mechanism of the synergistic anti-apoptosis function of proHB-EGF-CT and mBAG-1-UBH is still unknown. We offer a hypothesis that proHB-EGF-CT can maintain high levels of nuclear BAG-1. In this study, we first report the three-dimensional nuclear magnetic resonance structure of proHB-EGF-CT complexed with mBAG-1-UBH. In the structure of the complex, the residues in the C-terminus and one turn between β-strands β1 and β2 of mBAG-1-UBH bind to two terminals of proHB-EGF-CT, which folds into a loop with end-to-end contact. This end-to-end folding of proHB-EGF-CT causes the basic amino acids to colocalize and form a positively charged groove. The dominant forces in the binding interface between proHB-EGF-CT and mBAG-1-UBH are charge-charge interactions. On the basis of our mutagenesis results, the basic amino acid cluster in the N-terminus of proHB-EGF-CT is the crucial binding site for mBAG-1-UBH, whereas another basic amino acid in the C-terminus facilitates this interaction. Interestingly, the mBAG-1-UBH binding region on the proHB-EGF-CT peptide is also involved in the region found to be important for nuclear envelope targeting, supporting the hypothesis that proHB-EGF-CT is most likely able to trigger the nuclear translocation of BAG-1 in keeping its level high.
authors.affiliation: Instrumentation Center, National Tsing Hua University , Hsinchu 30013, Taiwan.
authors.forename: Kuo-Wei
authors.initials: KW
authors.lastname: Hung
authors.forename: Hsiao-Wen
authors.initials: HW
authors.lastname: Huang
authors.forename: Ching-Chang
authors.initials: CC
authors.lastname: Cho
authors.forename: Sheng-Chieh
authors.initials: SC
authors.lastname: Chang
authors.forename: Chin
authors.initials: C
authors.lastname: Yu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D003593:Cytoplasm / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019254:Genes, bcl-2; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C091732:BCL2-associated athanogene 1 protein; D004268:DNA-Binding Proteins; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D014157:Transcription Factors; D025801:Ubiquitin