Table 1

Discriminatory key to classify indecisive isoforms.
Characteristics	FeSOD	MnSOD

Metal specificity	Fe	Mn
Amino acid length	199–229	200–316
Theoretical molecular weight	21–25 KDa	22–34 KDa
No. of a helix*	13	14
No. of b strand*	3	3
Domains	N & C terminal	N & C terminal
Motif	DVWEHAYY	DVWEHAYY
Active site residues*	Fig 3	Fig 4
Structurally highly conserved metal specific residues	F₁₈₄XXXA₁₈₈Q_189.......T_280......F/Y₃₀₃	R₁₈₄XXXG₁₈₈G_189.......G_280......W₃₀₃
Conserved residue with photosynthetic role	K87, K139	None
Transmembrane hydrophobic pocket	Absent	Present

* – Based on the structural analysis of MnSOD of Anabaena sp. (PDB No: 1gv3) and FeSOD of Thermosynechococcus elongatus BP-1 (PDB No: 1my6)
Priya et al. BMC Genomics 2007 8:435 doi:10.1186/1471-2164-8-435