ClustalW alignment of the putative L-arginine deiminase Sll1336 of Synechocystis sp. PCC 6803 and the L-arginine deiminase ArcA from the primitive eukaryote Giardia intestinales. Both proteins share 43% overall similarity (10% identical, 19% strongly similar, 14% weakly similar amino acid residues. * Identical amino acid residues, : similar amino acid residues (A/V/F/P/M/I/L/W, D/E, R/H/K, S/T/Y/H/C/N/G/Q, and • weakly similar amino acid residues. Gaps were introduced into the sequences to maintain an optimal alignment. Two putative transmembrane helices of Sll0573 are boxed (see text for details).