Structural Insights into a Hemoglobin-Albumin Cluster in Aqueous Medium.
A hemoglobin (Hb) wrapped covalently by three human serum albumins (HSAs) is a triangular protein cluster designed as an artificial O2-carrier and red blood cell substitute. We report the structural insights into this Hb-HSA3cluster in aqueous medium revealed by 3D reconstruction based on cryogenic transmission electron microscopy (cryo-TEM) data and small-angle X-ray scattering (SAXS) measurements. Cryo-TEM observations showed individual particles with approximately 15 nm diameter in the vitrified ice layer. Subsequent image processing and 3D reconstruction proved the expected spatial arrangements of an Hb in the center and three HSAs at the periphery. SAXS measurements demonstrated the monodispersity of the Hb-HSA3cluster having a molecular mass of 270 kDa. The pair-distance distribution function suggested the existence of oblate-like particles with a maximum dimeter of ∼17 nm. The supramolecular 3D structure reconstructed from the SAXS intensity using an ab initio procedure was similar to that obtained from cryo-TEM data.
Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University , 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
Ryuichi
R
Shinohara
Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University , 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
Taiga
T
Yamada
Research Center of Electron Microscopy, Institute of Chemistry and Biochemistry, Freie Universität Berlin , Fabeckstrasse 36a, 14195 Berlin, Germany.
Boris
B
Schade
Research Center of Electron Microscopy, Institute of Chemistry and Biochemistry, Freie Universität Berlin , Fabeckstrasse 36a, 14195 Berlin, Germany.
Christoph
C
Böttcher
Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University , 3-15-1 Tokida, Ueda-shi, Nagano 386-8567, Japan.
Takaaki
T
Sato
Materials Characterization Central Laboratory, Waseda University , 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
Natsuhiko
N
Sugimura
Materials Characterization Central Laboratory, Waseda University , 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
Toshimichi
T
Shibue
Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University , 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
Teruyuki
http://orcid.org/0000-0002-7622-3433
T
Komatsu
D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D008970:Molecular Weight; D010100:Oxygen / Q000737:chemistry; D053838:Scattering, Small Angle; D000075462:Serum Albumin, Human / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014867:Water / Q000737:chemistry*
D006454:Hemoglobins; D014867:Water; D010100:Oxygen; D000075462:Serum Albumin, Human