Fig. 2. Phylogenetic analysis assigns many Drosophila SLC6 proteins to previously identified subfamilies and a novel IAAT subfamily. An unrooted phylogenetic tree displaying Drosophila candidate amino acid (AA) sequences with cloned and predicted SLC6 transporter amino acid sequences from multiple organisms. Candidate Drosophila SLC6 transporters are labelled in bold and underlined. Prominently represented among the insect sequences are putative SLC6s from Anopheles gambiae (Ag), a mosquito known for carrying the malaria parasite and whose genome sequence was recently reported (Holt et al., 2002). We also have included known transporter sequences from insects such as the cabbage looper, Trichoplusia ni (Tn), the tobacco caterpillar Manduca sexta (Ms) and from mammals. See Table S1 in supplementary material for a list of the sequence names, abbreviations and accession numbers. Subfamilies (monoamine transporters, GABA transporters, orphan neurotransmitter transporters, insect amino acid transporters) are indicated. As expected, a number of sequences do not group with the previously identified subfamilies. Many of the C. elegans transporters are quite divergent and group with each other; likewise, the prokaryote transporters are most similar to each other but do not segregate into a recognized subfamily with eukaryote transporters. Several of the candidate Drosophila transporters form a small subgroup that does not convincingly group with any other transporters. Nodes that are identical in >90% of bootstrap trials are denoted by filled circles and nodes that are identical in 75-90% of bootstrap trials are denoted by empty circles. The complete multiple sequence alignment from which this phylogenetic tree was generated is available as Fig. S1 in supplementary material.