FIG. 6.

Interaction between E₂₆₈ and the loop between β5 and α6. Residues from the loop (F₂₉₇ GAG₃₀₀ YS₃₀₂), E₂₆₈, and the two neighboring residues (D₂₉₅ and E₂₆₅) for Mg²⁺ ion (green ball) binding are highlighted to show that mutation of E₂₆₈ may affect Mg²⁺ and substrate binding.