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Journal Article

Effect of the ionic environment on the molecular structure of bacteriophage SPP1 portal protein

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons95648

Tichelaar,  Willem
Department of Cell Physiology, Max Planck Institute for Medical Research, Max Planck Society;

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Citation

Jekow, P., Behlke, J., Tichelaar, W., Lurz, R., Regalla, M., Hinrichs, W., et al. (1999). Effect of the ionic environment on the molecular structure of bacteriophage SPP1 portal protein. European Journal of Biochemistry, 264(3), 724-735. doi:10.1046/j.1432-1327.1999.00601.x.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-A676-2
Abstract
Bacteriophage SPP1 portal protein is a large cyclical homo-oligomer composed of 13 subunits. The solution structure and assembly behavior of this protein with high-point rotational symmetry was characterized. The purified protein was present as a monodisperse population of 13-mers, named gp6H, at univalent salt concentrations in the hundred millimolar range (>= 250 m m NaCl) or in the presence of bivalent cations in the millimolar range (>= 5 m m MgCl2). Gp6H had a slightly higher sedimentation coefficient, a smaller shape-dependent frictional ratio, and a higher rate of intersubunit cross-linking in the presence of magnesium than in its absence. In the absence of bivalent cations and at univalent salt concentrations below 250 m m, the 13-mer molecules dissociated partially into stable monomers, named gp6L. The monomer had a somewhat different shape from the subunit present in the 13-mer, but maintained a defined tertiary structure. The association-dissociation equilibrium was mainly between the monomer and the 13-mer with a minor population of intermediate oligomers. Their interconversion was strongly influenced by the ionic environment. Under physiological conditions, the concentration of Mg2+ found in the Bacillus subtilis cytoplasm (10-50 m m) probably promotes complete association of gp6 into 13-mer rings with a compact conformation