Bax-beta

Bax? is encoded by a 1.5 kb RNA species created by the retention of intron 5 in the bax mRNA transcript. The exon4/intron5 splice junction is evolutionarily conserved and is found in both the human and mouse bax coding regions. The 630 bp intron 5 contributes 60 amino acids to the Bax? protein before a stop codon is encountered during translation. The Bax? protein is 24 kDa in size and although it contains the BH1, BH2, and BH3 domains identical to Bax, it has a unique carboxyl terminus and does not have a hydrophobic transmembrane domain (Oltvai et al., 1993). Bax? mRNA has been found in many mouse tissues using RT-PCR. It is found co-expressed with Bax? in lung, stomach, kidney, thymus, lymph node, bone marrow, pancreas, and spleen. Bax? mRNA was very abundant in brain and duodenum with almost no Bax? mRNA detected in these tissues (Oltvai et al., 1993).