SNX20 and SNX21 share conserved PX and PXB/TPR domains.
A, sequence alignment and domain boundaries of mouse, human, and zebrafish SNX20 and SNX21. Secondary structure predictions were calculated with JPRED for the entire SNX20 sequence and the SNX21 PX domain, or determined from the crystal structure of the SNX21 PXB/TPR domain. These are indicated for SNX21 (above) and SNX20 (below). Green stars indicate point mutants generated for biochemical studies. B, SNX20 and SNX21 sequence alignment based on secondary structure predictions. Chordates and insect sequences were aligned using PRALINE (35). Residues predicted to form helical or extended structures are highlighted in red and blue, respectively. C, maximum likelihood phylogenetic tree for the SNX20 and SNX21 proteins, constructed in MEGA 5.1 with 1000 bootstrap test iterations (36). The tree was built with 10 chordates and 2 insects sequences, and was rooted using yeast Snx3p as an ancestral PX protein (red dot). The scale bar represents the genetic distance of protein members in a subtree from the corresponding node.