The highly conserved cytoplasmic domain of CD43 is constitutively phosphorylated in ex vivo murine T cells. (A) Purified ex vivo DO.11.10 T cells or (B) resting DO.11.10 T-cell lymphoblasts were labeled with [³²P] orthophosphate, incubated in the absence or presence of PMA (50 ng/mL) for the indicated time, and lysed. CD43 was immunoprecipitated separated by SDS-PAGE, and phosphorylation was detected by autoradiography. (C) Alignment of the CD43 cytoplasmic domain from human, chimpanzee, mouse, rat, cattle, and dog using ClustalW (version 1.8).⁴³  Numbering refers to the human sequence, with 1 indicating the start of the cytoplasmic domain. Numbering from the translational start site is indicated in parentheses. *Identical residues in all sequences in the alignment (shaded in black); “:” indicates conserved substitutions (shaded in gray), and “.” indicates semiconserved substitutions. Serine and threonine residues conserved across all species are denoted by ▾. Positions of murine Ser72 and Ser76 (corresponding to human Ser74 and Ser78) are indicated by † and ‡, respectively.