title: New protein purification system using gold-magnetic beads and a novel peptide tag, "the methionine tag".
abstract: Gold magnetic particles (GMP) are magnetic iron oxide particles modified with gold nanoparticles. The gold particles of GMP specifically bind to cysteine and methionine through Au-S binding. The aim of the present study was to establish a quick and easy protein purification system using novel peptide tags and GMP. Here, we created a variety of peptide tags containing methionine and cysteine and analyzed their affinity to GMP. Binding assays using enhanced green fluorescent protein (EGFP) as a model protein indicated that the tandem methionine tags comprising methionine residues had higher affinity to the GMP than tags comprising both methionine and cysteine residues. Tags comprising both methionine and glycine residues showed slightly higher affinity to GMP and higher elution efficiency than the all-methionine tags. A protein purification assay using phosphorylcholine-treated GMP demonstrated that both a tandem methionine-tagged EGFP and a methionine and glycine-tagged EGFP were specifically purified from a protein mixture with very high efficiency. The efficiency was comparable to that of a histidine-tagged protein purification system. Together, these novel peptide tags, "methionine tags", specifically bind to GMP and can be used for a highly efficient protein purification system.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka, Japan. okadabos@phs.osaka-u.ac.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Okada
authors.forename: Tomoko Y
authors.initials: TY
authors.lastname: Takano
authors.forename: Nozomi
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Arisa
authors.initials: A
authors.lastname: Hayashi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Yonekura
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Abe
authors.forename: Takuya
authors.initials: T
authors.lastname: Yoshida
authors.forename: Takao A
authors.initials: TA
authors.lastname: Yamamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Seino
authors.forename: Takefumi
authors.initials: T
authors.lastname: Doi
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D005290:Ferric Compounds / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000302:isolation & purification*; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D008715:Methionine / Q000737:chemistry*; D010316:Particle Size; D010455:Peptides / Q000737:chemistry*; D010767:Phosphorylcholine / Q000737:chemistry; D011485:Protein Binding; D013499:Surface Properties
chemical_list: D005290:Ferric Compounds; D010455:Peptides; C485184:enhanced green fluorescent protein; D010767:Phosphorylcholine; D049452:Green Fluorescent Proteins; C000499:ferric oxide; D006046:Gold; D008715:Methionine