title: Purification of human plasma haptoglobin by hemoglobin-affinity column chromatography.
abstract: Haptoglobin (Hp) is an acute-phase protein; its plasma levels increase consistently in response to infection and inflammation. The concentration of human plasma Hp is ranged between 1 and 1.5 mg/ml. Similar to blood type, individual human Hp is classified as Hp 1-1, 2-1, or 2-2. The structural and functional analysis of the Hp, however, has not been studied in detail due to its difficult isolation procedure. Previously, we reported a single step for the purification of porcine Hp. In this study, we established a purification method using a high capacity hemoglobin-affinity column. Briefly, DEAE-purified human hemoglobin was first coupled to Sepharose 4B to prepare an affinity column in a 15-ml bed volume. Following a flow through of human plasma and an extensive wash, the bound material was eluted with a solution of 0.15 M NaCl, pH 11 (adjusted by ammonium), to remove low-affinity bound proteins. The high-affinity bound Hp was then eluted with 0.15 M NaCl containing 5 M urea, pH 11, and collected in tubes containing 100 microl of 1 M Tris buffer, pH 7.0. The biological activity of dialyzed Hp was retained as it formed a complex with hemoglobin on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Using this procedure, approximately 10 mg of Hp 1-1, with homogeneity greater than 96%, was obtained from 15 ml of human plasma. Affinity purified Hp 2-1 or 2-2, however, contained trace amounts of apoA-I with the similar approach. The Hp could be further purified by HPLC using a Superose 12 gel-permeation chromatography, if desired, to achieve 100% purity. All the phenotypes of purified Hp consisted of alpha and beta chains on SDS-PAGE in the presence of a reducing reagent, further confirmed by a Western blot analysis. We conclude that human hemoglobin-affinity column was most suitable for the isolation of Hp 1-1 in large quantities. Whereas, one additional step using a gel-permeation was necessary for that of Hp 2-1 and 2-2.
authors.affiliation: Research Institute of Biochemical Engineering, Department of Biological Science and Technology, National Chiao Tung University, 75 Po-Ai Street, Hsinchu, Taiwan.
authors.forename: Chun Yi
authors.initials: CY
authors.lastname: Liau
authors.forename: Tsai Mu
authors.initials: TM
authors.lastname: Chang
authors.forename: Ju Pin
authors.initials: JP
authors.lastname: Pan
authors.forename: Wen Liang
authors.initials: WL
authors.lastname: Chen
authors.forename: Simon J T
authors.initials: SJ
authors.lastname: Mao
mesh_terms: D002846:Chromatography, Affinity / Q000379:methods*; D004591:Electrophoresis, Polyacrylamide Gel; D006242:Haptoglobins / Q000302:isolation & purification*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans
chemical_list: D006242:Haptoglobins; D006454:Hemoglobins