Formation of a Hexagonal Lattice Structure by an R-Form Lipopolysaccharide of Klebsiella

Effect of Various Divalent Cations on the Lattice Formation

Abstract

The R-form lipopolysaccharide from Klebsiella pneumoniae strain LEN-111 (O3-:K1-), from which cationic material had been removed by electrodialysis, was previously shown to form a hexagonal lattice structure with the lattice constant of 14 to 15nm when suspended in 50mM tris(hydroxymethyl)aminomethane buffer at pH 8.5 containing 10mM Mg²⁺. Under this experimental condition, effects of other divalent metal cations on the hexagonal assembly of the electrodialyzed LPS were compared with that of Mg²⁺. The Zn²⁺, Hg²⁺, Cu²⁺, and Ni²⁺ could produce essentially the same hexagonal lattice structure with the lattice constant of 14.5 to 15.0nm as that formed with Mg²⁺. The Cd²⁺, Co²⁺, and Fe²⁺ produced the hexagonal lattice structure with the lattice constant of 15.5 to 16.0nm, and Ba²⁺ Sr²⁺, and Ca²⁺ produced that with the lattice constant of 18 to 19nm. In addition, the hexagonal lattice structures formed with the latter three cations were less orderly than those formed with the other cations. When the higher concentrations of Ba²⁺, Sr²⁺, and Ca²⁺ were used, the lattice constants were not shortened. The length of lattice constants of the hexagonal lattice structures formed with the divalent cations did not relate to the quantity of the cations bound to the LPS. Among the divalent cations tested, Hg²⁺ was bound to the LPS in the smallest amount (its atomic ratio to P, 0.07), and Zn²⁺ and Fe²⁺ were bound in very large amounts (their atomic ratios to P, 2.94 and 8.28, respectively).