The second catalytic HKD motif and putative PIP2-binding sites in Arabidopsis and rice PLDs. A, multiple alignment of the second catalytic motif and adjacent regions harbouring alleged sites for PIP2 binding . Conserved amino acid residues are indicated by shading, asterisks denote the catalytic triad. Mutated residues of the catalytic motif in OsPLDθ are on the red background. Positions of conserved residues in the postulated PIP2-binding motifs are indicated by (x), basic residues are in bold. B, multiple alignment of a box conserved among all PLDs and known to bind PIP2 in mammalian and yeast PXPH-PLDs. Three arginine residues involved in PIP2 binding  are absolutely conserved in all PXPH-PLDs, but are not present in C2-PLDs. Motif positions are indicated by (#), arginine residues are in bold. The numbers at the right of individual sequences in both alignments refer to the position of the last residue within the whole protein, the question mark (?) indicate that complete protein sequence is not available. Species abbreviations are the same as used in the Fig. 1. See Additional files for accession numbers and other sequence information.