title: Structural basis for dimerization of the Dictyostelium gelation factor (ABP120) rod.
abstract: Gelation factor (ABP120) is one of the principal actin-cross-linking proteins of Dictyostelium discoideum. The extended molecule has an N-terminal 250-residue actin-binding domain and a rod constructed from six 100-residue repeats that have an Ig fold. The ability to dimerize is crucial to the actin cross-linking function of gelation factor and is mediated by the rod in which the two chains are arranged in an antiparallel fashion. We report the 2.2 A resolution crystal structure of rod domains 5 and 6, which shows that dimerization is mediated primarily by rod domain 6 and is the result of a double edge-to-edge extension of beta-sheets. Thus, contrary to earlier proposals, the chains of the dimeric gelation factor molecule overlap only within domain 6, and domains 1-5 do not pair with domains from the other chain. This information allows construction of a model of the gelation factor molecule and suggests how the chains in the related molecule filamin (ABP280) may interact.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Rd, Cambridge CB2 2QH, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: McCoy
authors.forename: P
authors.initials: P
authors.lastname: Fucini
authors.forename: A A
authors.initials: AA
authors.lastname: Noegel
authors.forename: M
authors.initials: M
authors.lastname: Stewart
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D003285:Contractile Proteins / Q000737:chemistry / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D004023:Dictyostelium / Q000737:chemistry*; D019281:Dimerization; D004583:Electrons; D064448:Filamins; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D016415:Sequence Alignment
chemical_list: D002352:Carrier Proteins; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; C060680:abpC protein, Dictyostelium