Computational analyses of protein coded by rice (Oryza sativa japonica) cDNA (GI: 32984786) indicate lectin like Ca2+ binding properties for Eicosapenta Peptide Repeats (EPRs)

Eicosapenta peptide repeats (EPRs) occur exclusively in flowering plant genomes and exhibit very high amino acid residueconservation across occurrence. DNA and amino acid sequence searches yielded no indications about the function due to absenceof similarity to known sequences. Tertiary structure of an EPR protein coded by rice (Oryza sativa japonica) cDNA (GI: 32984786)was determined based on ab initio methodology in order to draw clues on functional significance of EPRs. The resultant structurecomprised of seven α-helices and thirteen anti-parallel β-sheets. Surface-mapping of conserved residues onto the structure deducedthat (i) regions equivalent to β α4-the primary function of EPR protein could be Ca²⁺ binding, and (iii) the putative EPR Ca²⁺ binding domain is structurally similar tocalcium-binding domains of plant lectins. Additionally, the phylogenetic analysis showed an evolving taxa-specific distribution ofEPR proteins observed in some GNA-like lectins.