Molecular Cloning and Expression of Murine Thromboxane Synthase

The complementary DNA (cDNA) for murine thromboxane synthase (TS) was isolated from a lung cDNA library. The full-length cDNA (1,910 bp) encodes a 533 amino acid protein (Mr 58,220) sharing 78% identity with human TS. Sequence comparison indicated that one of the two N-glycosylation sites, eight of the eleven cysteine residues, and a heme-binding domain are conserved in both murine and human TS sequences. The authenticity of the cDNA was confirmed by transient expression of a catalytically active TS in cos-1 cells. Northern analysis indicated that murine TS gene was expressed primarily in lung, kidney, and spleen. Interestingly, the size of mRNA in the kidney was ∼ 100 to 150 bp shorter than that in the lung or spleen (2.2 Kb). RT-PCR and restriction mapping indicated that neither the coding sequence nor the 3′ untranslated region could account for the observed size difference, suggesting a shorter 5′ untranslated region and/or poly (A) tail in the kidney transcript.