Mutagenesis of conserved regions of murine STAT5A. Amino acid sequence alignment of the central region of several mammalian (H, human; M, mouse; R, rat) STAT family members is shown. Numbering is from the amino terminus, and alignment was performed by the program PRETTY.PILEUP (GCG, University of Wisconsin). The consensus sequence is given at the bottom; a capital letter indicates a highly conserved amino acid (at least 8 of 12 members). The numbering at the top of each panel refers to the consensus sequence and because of gaps in the homology is not correct for STAT5A. The positions of the canonical Src homology 2 (SH2) domain and the putative DNA-binding domain as defined by Horvath et al57 are indicated by the shaded boxes, whereas the conserved JAK phosphorylation site is indicated by the arrowhead. The locations of the alanine substitution mutations WKR→AAA, RQQ→AAA, EE→AA, and VVV→AAA are indicated by bold face A characters below the sequence. The positions of insertion of termination codons in the murine STAT5A C-terminal truncation mutants ▵53C (this report), ▵683,23 ▵749,24 ▵713,25 and ▵65049 are shown by arrowheads.