title: RNA and protein complexes of trp RNA-binding attenuation protein characterized by mass spectrometry.
abstract: We have characterized both wild-type and mutant TRAP (trp RNA-binding attenuation protein) from Bacillus stearothermophilus , and their complexes with RNA or its regulator anti-TRAP protein (AT), by electrospray ionization mass spectrometry (ESI-MS). Wild-type TRAP mainly forms homo-11mer rings. The mutant used carries three copies of the TRAP monomer on a single polypeptide chain so that it associates to form a 12mer ring with four polypeptide molecules. Mass spectra showed that both the wild-type TRAP 11mer and the mutant TRAP 12mer can bind a cognate single-stranded RNA molecule with a molar ratio of 1:1. The crystal structure of wild-type TRAP complexed with AT shows a TRAP 12mer ring surrounded by six AT trimers. However, nanoESI-MS of wild-type TRAP mixed with AT shows four species with different binding stoichiometries, and the complex observed by crystallography represents only a minor species in solution; most of the TRAP remains in an 11mer ring form. Mass spectra of mutant TRAP showed only a single species, TRAP 12mer + six copies of AT trimer, which is observed by crystallography. These results suggest that crystallization selects only the most symmetrical TRAP-AT complex from the solution, whereas ESI-MS can take a "snapshot" of all the species in solution.
authors.affiliation: Yokohama City University, Supramolecular Biology, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan. akashi@tsurumi.yokohama-cu.ac.jp
authors.forename: Satoko
authors.initials: S
authors.lastname: Akashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Watanabe
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Heddle
authors.forename: Satoru
authors.initials: S
authors.lastname: Unzai
authors.forename: Sam-Yong
authors.initials: SY
authors.lastname: Park
authors.forename: Jeremy R H
authors.initials: JR
authors.lastname: Tame
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001411:Geobacillus stearothermophilus / Q000378:metabolism; D009154:Mutation; D012313:RNA / Q000737:chemistry*; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; C079092:MtrB protein, Bacteria; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D012313:RNA; D014364:Tryptophan