FIG. 2.

Molecular cloning of human PTPLB cDNAs. (A) Representative clones covering the full-length cDNA of the PTPLB gene are shown. An asterisk indicates the translation stop codon. The open box represents the open reading frame identified in the two-hybrid screen; the 5′ and 3′ untranslated sequences were determined by 5′- and 3′-RACE and expressed sequence tag human GenBank overlaps. (B) PTPLB is composed of six exons. The locations of the six exons are indicated. (C) Proposed topology of PTPLB in the ER membrane, as predicted by hydropathy, the “positive inside” rule, and the known cytosolic disposition of C-terminal ER retention signals (see reference 34). (D) Nucleotide and deduced amino acid sequences of human PTPLB. The amino acid sequences are shown in the single-letter code. The translation stop codon is indicated by an asterisk. The PTPase homology motifs, HCXXGXXRS and an aspartic acid (D), are indicated by bold letters, and the proline that replaces the catalytic arginine is bold and underlined. The C-terminal ER retention motif, KKFE, is in bold. Four transmembrane segments are predicted by hydropathy plot analysis, performed with the TMHMM software, and the sequences are indicated by the heavy underlines.