FIG. 3.

Comparison of zinc contents among the WT LF and its mutants (A) and the positions of residue His-669 and Zn²⁺ (B). Residues His-686 and His-690 formed a zinc binding motif, HEXXH. Their distance to Zn²⁺ is within 3 Å. Residue His-669 is far from Zn²⁺, implying that it is impossible for this residue to be involved in Zn²⁺ stabilization.