Characterization of a noncovalent lipocalin complex by liquid chromatography/electrospray ionization mass spectrometry.
Nanoscale liquid chromatography coupled to electrospray ionization mass spectrometry was used to identify the nature of the ligand that binds noncovalently to siderocalin (lipocalin 2). The folded state siderocalin-ligand complex was separated from free, unfolded siderocalin using reversed phase chromatography, and the molecular weight of the siderocalin ligand was then determined from the deconvoluted molecular weights of the complex and of the free protein. The ligand was identified as dihydroxybenzoyl-serine, a breakdown product of enterobactin, an iron-chelating compound ("siderophore") synthesized in bacteria. These results demonstrate that, in some cases, electrostatic noncovalent protein complexes can survive the denaturing conditions of reversed phase liquid chromatography and the gas phase transfer occurring during electrospray ionization.
Mass Spectrometry Center, Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA, 98195, USA. doneanu@u.washington.edu
Catalin E
CE
Doneanu
Roland K
RK
Strong
William N
WN
Howald
D000595:Amino Acid Sequence; D017306:Annexin A2 / Q000737:chemistry* / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
D017306:Annexin A2; D008024:Ligands