title: Self-polymerization of archaeal RadA protein into long and fine helical filaments.
abstract: The Archaeal protein RadA, a RecA/Rad51 homolog, is able to promote pairing and exchange of DNA strands with homologous sequences. Here, we have expressed, purified, and crystallized the catalytically active RadA protein from Sulfolobus solfataricus (Sso). Preliminary X-ray analysis indicated that Sso RadA protein likely forms helical filament in protein crystals. Using atomic force microscopy with a carbon nanotube (CNT) tip for high-resolution imaging, we demonstrated that Sso RadA protein indeed forms fine helical filaments up to 1 microm in length ( approximately 10nm pitch) in the absence of DNA and nucleotide cofactor. We also observed that Sso RadA protein helical filament could dissemble upon incubation with ssDNA, and then the proteins associate with ssDNA to form nucleoprotein filament.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, ROC.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Lee
authors.forename: Chih-Hsiang
authors.initials: CH
authors.lastname: Leng
authors.forename: Yuan-Chih
authors.initials: YC
authors.lastname: Chang
authors.forename: Chia-Cheng
authors.initials: CC
authors.lastname: Chou
authors.forename: Yi-Kai
authors.initials: YK
authors.lastname: Chen
authors.forename: Fu-Fei
authors.initials: FF
authors.lastname: Hsu
authors.forename: Chia-Seng
authors.initials: CS
authors.lastname: Chang
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
authors.forename: Ting-Fang
authors.initials: TF
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D003460:Crystallization / Q000379:methods*; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000648:ultrastructure*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D019281:Dimerization; D008969:Molecular Sequence Data; D011108:Polymers / Q000138:chemical synthesis; D011485:Protein Binding; D011487:Protein Conformation; D016944:Sulfolobus / Q000201:enzymology*
chemical_list: D019843:Archaeal Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D011108:Polymers; C117252:RadA protein, archaeal