title: Precipitation by lanthanum ions: a straightforward approach to isolating phosphoproteins.
abstract: Posttranslational modification (PTM) of proteins, particularly phosphorylation, is a key element in the regulation of cell functions. In many signal transduction processes, PTM is a pivotal step. Various analytical methods have been proposed for the identification of phosphoproteins; however, most of these methods require sophisticated equipment. Here we present an easily applicable method of phosphoprotein enrichment. This method is based on single-step precipitation by lanthanum chloride and allows subsequent protein identification by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-TOF-MS). The method proved its suitability for the isolation of phosphoproteins from frozen tissue and cultured cells samples after cell lysis in various buffer systems (urea/thiourea and EGTA/EDTA). The tests revealed that the isolation of phosphoproteins can be achieved with high efficiency even from complex protein mixtures. Our results indicate that lanthanum-based enrichment of phosphoproteins can be a useful tool in phosphoproteomic studies.
authors.affiliation: Institute of Hygiene and Occupational Medicine, University Hospital Essen, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Pink
authors.forename: Nisha
authors.initials: N
authors.lastname: Verma
authors.forename: Fabio
authors.initials: F
authors.lastname: Polato
authors.forename: Günther K
authors.initials: GK
authors.lastname: Bonn
authors.forename: Hideo A
authors.initials: HA
authors.lastname: Baba
authors.forename: Albert W
authors.initials: AW
authors.lastname: Rettenmeier
authors.forename: Simone
authors.initials: S
authors.lastname: Schmitz-Spanke
mesh_terms: D000818:Animals; D002417:Cattle; D004527:Egg Proteins / Q000302:isolation & purification; D007811:Lanthanum / Q000737:chemistry*; D008894:Milk Proteins / Q000302:isolation & purification; D010750:Phosphoproteins / Q000302:isolation & purification*; D011499:Protein Processing, Post-Translational; D040901:Proteomics / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013552:Swine
chemical_list: D004527:Egg Proteins; D008894:Milk Proteins; D010750:Phosphoproteins; C028521:lanthanum chloride; D007811:Lanthanum