Fig. 1. The predicted domain structure of TagA Similarity searches of the predicted amino acid sequence of the tagA gene suggests an amino-terminal serine protease domain and a carboxyl-terminal ABC transporter domain. A. Amino acid residues known to be required for protease activity are indicated by their single letter code and position. PR1 and PR2 represent regions of the gene that were used as probes for library screening and RNase protection assays. The position of a blasticidin resistance cassette (Bsr) insertion at the nucleotide binding site is also shown. B. Kyte-Doolittle hydropathy plot showing location of probable membrane-spanning regions within the ABC transporter domain (black bar). C. Sequence alignment of the deduced amino acid sequences for the predicted serine protease domains TagA and TagC. D. Sequence alignment of the deduced amino acid sequences for the predicted ABC transporter domains of Dictyostelium TagA, TagC, human ABCB.3 (Tap2) and human ABCB.1 (Hmdr1).