| Abstract: | The cell surface glycoprotein of Halobacterium halobium is soluble in dilute buffer at neutral pH. At low counterion concentrations, the protein is monomeric (Ms,D = 209 kDa) and exhibits the characteristics of a highly charged polyelectrolyte. Evidence obtained from intrinsic fluorescence and far-UV circular dichroism shows that the monomer at low salt loses both its native conformation and its inherent tendency to form high molecular mass assemblies. In 4M NaCl, 25 mM KCl, and in the presence of divalent ions (greater than or equal to 50mM Mg2+ or Ca2+), association to well-defined assemblies of up to approximately 4 X 10(6) Da occurs. At low Mg2+ concentration and in the presence of Ba2+, a wide size-distribution of aggregates is observed. The assembly pattern of the protein may be correlated with salt-dependent alterations in the morphology of the bacterium. |
