The interaction of magnesium ions with teichoic acid

Area of Science:

• Microbiology
• Biochemistry
• Biophysical Chemistry

Background:

• Wall teichoic acids are crucial anionic polymers in Gram-positive bacterial cell walls.
• Understanding cation binding to teichoic acids is vital for comprehending cell wall structure and function.

Purpose of the Study:

• To quantify the binding of magnesium ions (Mg2+) to wall teichoic acid from Lactobacillus buchneri.
• To investigate the influence of pH, ionic strength, and competing cations on Mg2+ binding.

Main Methods:

• Equilibrium dialysis was employed to measure Mg2+ binding.
• Experiments were conducted under controlled ionic concentration and pH conditions.

Main Results:

• One Mg2+ ion bound per two phosphate groups of teichoic acid at pH 5.0 in 10mM NaCl, with an association constant (Kassoc.) of 2.7 x 10(3) M-1.
• Mg2+ binding decreased with decreasing pH below the phosphate pKa, correlating with phosphate group ionization.
• Ca2+ competed with Mg2+ for binding sites, significantly reducing Mg2+ association. Increased NaCl concentration also reduced binding.

Conclusions:

• Mg2+ binding to teichoic acid is sensitive to environmental conditions like pH and ionic strength.
• Cation competition, particularly with Ca2+, plays a significant role in modulating Mg2+ binding to teichoic acid.
• These findings provide insights into the role of teichoic acid in Gram-positive bacterial cell wall organization and cation homeostasis.