Solution Structure of the Cytohesin-1 (B2-1) Sec7 Domain and Its Interaction with the GTPase ADP Ribosylation Factor 1

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 14; pp. 7909 - 7914
• Main Authors: Betz, Stephen F., Schnuchel, Arndt, Wang, Hong, Olejniczak, Edward T., Meadows, Robert P., Lipsky, Brian P., Edith A. S. Harris, Staunton, Donald E., Fesik, Stephen W.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 07.07.1998; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences
• Subjects: ADP-Ribosylation Factors; Amino Acid Sequence; Atoms; Binding Sites; Biochemistry; Biological Sciences; Biological Transport; CD18 Antigens - metabolism; Cell Adhesion Molecules - chemistry; Cell Adhesion Molecules - metabolism; Cells; Chemical equilibrium; Cloning, Molecular; Drug interactions; Genes; Grants; GTP-Binding Proteins - metabolism; Guanine Nucleotide Exchange Factors; Humans; Integrins; Mathematical helices; Molecular Sequence Data; Mutant proteins; Nucleotides; Protein Binding; Protein Folding; Protein Structure, Secondary; Proteins
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.14.7909

Cytohesin-1 (B2-1) is a guanine nucleotide exchange factor for human ADP ribosylation factor (Arf) GTPases, which are important for vesicular protein trafficking and coatamer assembly in the cell. Cytohesin-1 also has been reported to promote cellular adhesion via binding to the β 2 integrin cytoplasmic domain. The solution structure of the Sec7 domain of cytohesin-1, which is responsible for both the protein's guanine nucleotide exchange factor function and β 2 integrin binding, was determined by NMR spectroscopy. The structure consists of 10 α -helices that form a unique tertiary fold. The binding between the Sec7 domain and a soluble, truncated version of human Arf-1 was investigated by examining1H-15N and1H-13C chemical shift changes between the native protein and the Sec7/Arf-1 complex. We show that the binding to Arf-1 occurs through a large surface on the C-terminal subdomain that is composed of both hydrophobic and polar residues. Structure-based mutational analysis of the cytohesin-1 Sec7 domain has been used to identify residues important for binding to Arf and for mediating nucleotide exchange. Investigations into the interaction between the Sec7 domain and the β 2 integrin cytoplasmic domain suggest that the two proteins do not interact in the solution phase.