title: Analysis of effect of casein phosphopeptides on zinc binding using mass spectrometry.
abstract: Phosphorylation is one of the key events in signal transduction and zinc plays an important catalytic and/or structural role in many biological systems. The binding of Zn to a phosphopeptide will alter the physiological functions of a peptide. The binding of casein phosphopeptides (CPPs) to Zn has been analyzed using nanospray mass spectrometry. Electrospray ionization (ESI) spectra of peptides produced by tryptic digestion of alpha-casein incubated with Zn show both free and Zn-bound phosphopeptides. The interaction of CPPs and the corresponding dephosphorylated peptides with zinc is compared. This study demonstrates that the phosphorylation state of a peptide dramatically affects Zn binding, with the decrease in Zn-bound forms of peptide paralleling the decrease in phosphorylation as casein is chemically dephosphorylated, although, in some cases, a small amount of residual Zn-binding capacity remains in the completely dephosphorylated peptide. The observed fragmentation patterns of the Zn-bound CPPs support the thesis that nonphosphorylated residues are involved in the metal binding.
authors.affiliation: McMaster Regional Centre for Mass Spectrometry, Department of Chemistry, McMaster University, 1280 Main St. W., Hamilton, Ont. L8S 4M1, Canada. jwang@mcmaster.ca
authors.forename: Jiaxi
authors.initials: J
authors.lastname: Wang
authors.forename: Kirk
authors.initials: K
authors.lastname: Green
authors.forename: Graham
authors.initials: G
authors.lastname: McGibbon
authors.forename: Brian
authors.initials: B
authors.lastname: McCarry
mesh_terms: D002364:Caseins / Q000737:chemistry*; D036103:Nanotechnology; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry*; D010766:Phosphorylation; D011485:Protein Binding; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D015032:Zinc / Q000737:chemistry*
chemical_list: D002364:Caseins; D010748:Phosphopeptides; D015032:Zinc