Ej. Woo et al., Germin is a manganese containing homohexamer with oxalate oxidase and superoxide dismutase activities, NAT ST BIOL, 7(11), 2000, pp. 1036-1040
Germin is a hydrogen peroxide generating oxalate oxidase with extreme therm
al stability; it is involved in the defense against biotic and abiotic stre
ss in plants. The structure, determined at 1.6 Angstrom resolution, compris
es beta -jellyroll monomers locked into a homohexamer (a trimer of dimers),
with extensive surface burial accounting for its remarkable stability. The
germin dimer is structurally equivalent to the monomer of the 7S seed stor
age proteins (vicilins), indicating evolution from a common ancestral prote
in. A single manganese ion is bound per germin monomer by ligands similar t
o those of manganese superoxide dismutase (MnSOD). Germin is also shown to
have SOD activity and we propose that the defense against extracellular sup
eroxide radicals is an important additional role for germin and related pro
teins.