title: Solution structure of the cytohesin-1 (B2-1) Sec7 domain and its interaction with the GTPase ADP ribosylation factor 1.
abstract: 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 beta2 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 beta2 integrin binding, was determined by NMR spectroscopy. The structure consists of 10 alpha-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 examining 1H-15N and 1H-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 beta2 integrin cytoplasmic domain suggest that the two proteins do not interact in the solution phase.
authors.affiliation: Pharmaceutical Discovery Division, Abbott Laboratories, Abbott Park, IL 60064, USA.
authors.forename: S F
authors.initials: SF
authors.lastname: Betz
authors.forename: A
authors.initials: A
authors.lastname: Schnuchel
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: E T
authors.initials: ET
authors.lastname: Olejniczak
authors.forename: R P
authors.initials: RP
authors.lastname: Meadows
authors.forename: B P
authors.initials: BP
authors.lastname: Lipsky
authors.forename: E A
authors.initials: EA
authors.lastname: Harris
authors.forename: D E
authors.initials: DE
authors.lastname: Staunton
authors.forename: S W
authors.initials: SW
authors.lastname: Fesik
mesh_terms: D020727:ADP-Ribosylation Factors; D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D018821:CD18 Antigens / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; D020662:Guanine Nucleotide Exchange Factors; C100723:cytohesin-1; D019204:GTP-Binding Proteins; D020727:ADP-Ribosylation Factors