Molecular cloning and expression of novel sulphotransferase-like cDNAs from human and rat brain.
The sulphotransferase (SULT) gene family is involved with the conjugation of many small drugs, xenobiotics and endogenous compounds. In this report, we describe the cloning and expression of novel cDNAs from human and rat brain, which are structurally related to the SULTs. These cDNAs have been termed 'brain sulphotransferase-like' (BR-STL), because of their similarity to the SULTs and their selective expression in brain tissue. The proteins encoded by the human and rat BR-STL cDNAs (hBR-STL-1 and rBR-STL cDNA respectively), denoted as hBR-STL and rBR-STL, are 98% identical and 99% similar in sequence. The hBR-STL-1 cDNA contains an 852-nt open reading frame encoding a 284-amino-acid protein with a calculated molecular mass of 33083 Da. Northern-blot analyses of RNA isolated from eight human tissues indicate that the hBR-STL message is selectively expressed in brain. Characterization of different brain regions showed that message levels were highest in cortical brain regions. rBR-STL message levels were relatively low in brains of 1-day-old male and female rats, but increased to adult levels in RNA from 7-day-old rats, and remained at that level in adult animals. The hBR-STL and rBR-STL cDNAs were expressed in both Escherichia coli and Sf9 insect cells in the presence or absence of an N-terminal histidine-affinity tag (His-tag). Polyclonal antibodies were raised in chickens against purified His-tagged hBR-STL, and were used to detect the presence of rBR-STL in adult male and female rat brain cytosol. The high degree of sequence conservation, and the selective localization of the BR-STL message in brain, suggest an important function in the central nervous system.