Structural and functional studies of plant Polyamine Oxidase

Intracellular polyamine contents are regulated not only by biosynthesis and transport but also by catabolism through FAD dependent polyamine oxidases (PAOs). The results of various studies on PAO proteins in developmental processes and response to environmental stresses confirm the importance of this protein in plant life; however, there is no comprehensive study of phylogenetic and structural relationships of plant PAOs. In the present study, to better understand phylogenetic and structural relationships of PAO proteins, bioinformatics analyses were performed on 58 PAO protein sequences of 15 different plant species. Multiple clusters with gene duplications were identified in both dicot and monocot-species. According to the conserved motifs obtained by MEME and MAST tools, four motifs were similar in most plant species. As there is no structural information available on PAOs, structural analyses were carried out on PAOs from Oryza sativa and Arabidopsis thaliana as representative of monocot and dicot plants, respectively. Secondary structure analysis revealed that alpha helix dominated among secondary structure elements followed by random coils, extended strand and beta turns for all sequences. Tertiary structures were predicted with SWISS-MODEL server. The best templates with high similarity that their structure determined by experimental methods were selected. To our knowledge, this is the first report of phylogenetic and structural relationships of plant PAOs. Our results may provide a theoretical basis for future studies of functional and structural details of plants PAOs.