Miranda cargo-binding domain forms an elongated coiled-coil homodimer in solution: implications for asymmetric cell division in Drosophila.
Miranda is a multidomain adaptor protein involved in neuroblast asymmetric division in Drosophila melanogaster. The central domain of Miranda is necessary for cargo binding of the neural transcription factor Prospero, the Prospero-mRNA carrier Staufen, and the tumor suppressor Brat. Here, we report the first solution structure of Miranda central "cargo-binding" domain (residues 460-660) using small-angle X-ray scattering. Ab initio modeling of the scattering data yields an elongated "rod-like" molecule with a maximum linear dimension (D(max)) of approximately 22 nm. Moreover, circular dichroism and cross-linking experiments indicate that the cargo-binding domain is predominantly helical and forms a parallel coiled-coil homodimer in solution. Based on the results, we modeled the full-length Miranda protein as a double-headed, double-tailed homodimer with a long central coiled-coil region. We discuss the cargo-binding capacity of the central domain and propose a structure-based mechanism for cargo release and timely degradation of Miranda in developing neuroblasts.
Yousef
Mohammad S
MS
Structural Biology Research Center, Photon Factory, IMSS, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan. yousef@post.kek.jp
Kamikubo
Hironari
H
Kataoka
Mikio
M
Kato
Ryuichi
R
Wakatsuki
Soichi
S
D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D019281:Dimerization; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D053838:Scattering, Small Angle; D012996:Solutions; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; C107613:Mira protein, Drosophila; D012996:Solutions