Figure 2

Sequence logos of cyanobacterial PORs and diatom POR1 and POR2 proteins. Alignment of sequence logos of cyanobacterial POR proteins with diatom POR1 and POR2 proteins. Amino acid position indicated at the right of each line, corresponding to cyanobacterium Synechocystis elongatus and diatom Phaeodactylum tricornutum. Boxes indicate characteristic motifs, with diagnostic amino acids marked with asterisks: (a) Rossman fold essential to NADPH binding; (b) Y, K residues essential to enzyme-cofactor-substrate coordination and proton donation; (c) cysteine essential to catalysis. Amino acids are colored according to their chemical properties: green are polar (GSTYC); purple are neutral (QN), blue are positively charged (KRH); red are negatively charged (DE); and black are hydrophobic (AVLIPWFM).