Small-angle neutron scattering reveals an oxygen-dependent conformational change of the immunogen keyhole limpet hemocyanin type 1 (KLH1)

Abstract

The respiratory protein of the keyhole limpet, Megathura crenulata, the hemocyanin (KLH), commonly used as an immunogen, binds oxygen cooperatively, which implies the existence of different conformations. For the first time, two different conformations of KLH1 were detected upon oxygenation, a deoxy and an oxy state, using small-angle neutron scattering. Rearrangements in the quaternary structure of KLH1 were predicted from the different radii of gyration and the shifts of the minima and maxima in the scattering curves. Upon oxygenation, KLH1 becomes smaller and more compact. Model reconstruction of KLH1 indicates a hollow cylinder with two rings located close to both ends, which move slightly together upon oxygenation.

Small-angle X-ray Scattering-based Three-dimensional Reconstruction of the Immunogen KLH1 Reveals Different Oxygen-dependent Conformations

“…The radii of gyration were determined from the SAXS data to be 163.8 Ϯ 0.3 and 164.7 Ϯ 0.3 Å for oxygenated and deoxygenated KLH1, respectively. These values are in good agreement with the values recently determined by small-angle neutron scattering, 163.7 Ϯ 0.5 Å for oxygenated and 165.0 Ϯ 0.6 Å for deoxygenated KLH1 (32). Again, KLH1 seems to be slightly more compact in the oxygenated than in the deoxygenated state.…”

Keyhole Limpet Hemocyanin: 9-Å CryoEM Structure and Molecular Model of the KLH1 Didecamer Reveal the Interfaces and Intricate Topology of the 160 Functional Units

“…Another unexplored field constitutes oxygenation-dependent conformational changes in the quaternary structure. 55 Ultimately, to complete the molluscan hemocyanin picture, it might also be worthwhile to study the didecamers and multidecamers of KLH2 by cryoEM.…”

Modeling techniques for analysing conformational transitions in hemocyanins by small-angle scattering of X-rays and neutrons

“…Here, we present two methodical approaches with SAS to obtain information on the large cooperative hemocyanins and their structural transitions when binding the ligand dioxygen or allosteric effectors: (a) A rigid body modelling was developed and used to reconstruct n £ 6-meric hemocyanins and to investigate different conformations of the oxy-and deoxystates (Hartmann and Decker, 2002) and conformation changes induced by effectors such as lactate (Hartmann et al, 2001b). (b) A newly developed Monte-Carlo annealing algorithm (MCSAS) was applied to SAXS and SANS data to determine the conformations of the molluscan hemocyanin KLH1 in the oxy-and the deoxystate (Hartmann et al, 2001a;Hartmann and Decker, 2003;Hartmann et al, 2004).…”