FIG. 1.

K5 and mutant constructs. (A) The K5 protein is made up of three main modules as schematically represented in the center, with single-letter amino acid sequences shown for selected regions. At the N termini there is a C₄HC₃ RING-CH domain followed by two membrane-spanning domains (Tm). Carboxy terminal from the TMs is a CR. This conserved region is made up of a tyrosine-based motif (Tyr motif), a CM, a potential SH3B, and two stretches of acidic amino acids (DE1 and DE2). Numbering indicates the position within the K5 amino acid sequence, and letters above and below indicate residues that were mutated and the residue to which they were changed. Bars above or below the residues indicate mutant forms that contain mutations of multiple residues. (B) Expression of wild-type K5 proteins or each of the constructs was examined in stable BJAB cells. Normalized lysates were produced from each cell line and subjected to SDS-PAGE followed by Western blotting with an antibody against the V5 epitope tag encoded at the carboxy terminus of each construct.