Small-angle X-ray scattering-based three-dimensional reconstruction of the immunogen KLH1 reveals different oxygen-dependent conformations.
For decades the respiratory protein keyhole limpet hemocyanin (KLH1) from the marine gastropod Megathura crenulata has been used widely as a potent immunostimulant, useful hapten carrier, and valuable agent in the treatment of bladder carcinoma. Although much information on the immunological properties of KLH1 is available, biochemical and structural data are still incomplete. Small-angle x-ray scattering revealed the existence of two conformations, an oxy state being slightly more compact than the deoxy state. Based on small-angle scattering curves, a newly developed Monte Carlo algorithm delivered a surface representation of proteins. The massive changes of the surfaces of reconstructed didecameric KLH1 molecules are explained as a twist of the two non-covalently associated decameric half-molecules. Upon oxygenation, the KLH1 molecule becomes longer and skinnier. This study provides the first real evidence how a molluscan hemocyanin changes conformation during an allosteric transition.
Institut für Molekulare Biophysik, Universität Mainz, D-55099 Mainz, Germany. hartmann@biophysik.biologie.uni-mainz.de
Hermann
H
Hartmann
André
A
Bongers
Heinz
H
Decker
D000494:Allosteric Regulation; D000818:Animals; D000941:Antigens / Q000737:chemistry; D018360:Crystallography, X-Ray; D006433:Hemocyanins / Q000737:chemistry* / Q000378:metabolism; D008854:Microscopy, Electron; D008958:Models, Molecular; D008974:Mollusca / Q000737:chemistry / Q000276:immunology; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D012542:Scattering, Radiation
D000941:Antigens; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin; D010100:Oxygen