title: Characterization of horse spleen apoferritin reactive lysines by MALDI-TOF mass spectrometry combined with enzymatic digestion.
abstract: Ferritins are a class of iron storage protein spheres found mainly in the liver and spleen, which have attracted many research interests due to their unique structural features and biological properties. Recently, ferritin and apoferritin (ferritin devoid of the iron core), have been employed as chemically addressable nanoscale building blocks for functional materials development. However, the reactive residues of apoferritin or ferritin have never been specified and it is still unclear about the chemoselectivity of apoferritin towards different kinds of bioconjugation reagents. In this work, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry combined with enzymatic digestion analysis was used to identify the reactive lysine residues of horse spleen apoferritin when conjugated with N-hydroxysuccinimide reagents. The result demonstrated that among all the lysine residues, K97, K83, K104, K67 and K143 are the reactive ones that can be addressed.
authors.affiliation: Department of Chemistry and Biochemistry and Nanocenter, University of South Carolina, 631 Sumter Street, Columbia, SC 29208, USA. qing_zeng@hotmail.com
authors.forename: Qingbing
authors.initials: Q
authors.lastname: Zeng
authors.forename: Rachel
authors.initials: R
authors.lastname: Reuther
authors.forename: Jerry
authors.initials: J
authors.lastname: Oxsher
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001052:Apoferritins / Q000737:chemistry* / Q000378:metabolism; D006736:Horses; D008239:Lysine / Q000737:chemistry*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013154:Spleen / Q000737:chemistry*; D014357:Trypsin / Q000494:pharmacology*
chemical_list: D001052:Apoferritins; D014357:Trypsin; D008239:Lysine