FIGURE 4.

Conservation of AP-1 and AP-3 residues potentially involved in interactions with (D/E)XXXL(L/I) signals. A, alignment of human σ1A (RefSeq accession no. NP_001274), σ2 (GenBank^TM accession no. AAH06337), and σ3A (GenBank^TM accession no. CAG29337). The alignment shows the conservation of σ2 residues (Arg¹⁵, Ala⁶³, Val⁸⁸, Asn⁹², Glu¹⁰⁰, Leu¹⁰¹, and Leu¹⁰³ shown in black boxes) that interact with residues at different positions of the CD4 Q-peptide (20). Shown in black lettering are the positions on the signal (residue at −4; LL, dileucine pair; or O, other) proposed to bind to the σ residues in the corresponding boxes. B, alignment of N-terminal sequences of human γ1 (GenBank^TM accession no. AAH36283), αC (Swiss-Prot accession no. O94973) and δ (GenBank^TM accession number AAC51761) showing the conservation of the α subunit Arg residue (αArg¹⁵, shown in the black box) proposed to stabilize the −4 position of the CD4 Q-peptide (20). Alignments were generated with CLC Sequence Viewer; decreasing conservation of residues is shown by red to blue rainbow coloring.