FUNCTIONAL EXPRESSION OF CDNAS FOR BOVINE 11-BETA-HYDROXYLASE-ALDOSTERONE SYNTHASES, P450(11-BETA)-2 AND P450(11-BETA)-3 AND THEIR CHIMERAS

Two molecular species of bovine P450(11-beta), P450(11-beta)-2 and P450(11-beta)-3 have been identified, in which the amino acid differences were found at the 6th, 36th and 82nd positions from the NH2-termini of the mature proteins. They catalyzed the 11-beta-, 18- and 19-hydroxylation and aldosterone formation from 11-deoxycorticosterone, and the rate of production of 18-hydroxycorticosterone and aldosterone by P450(11-beta)-3 was greater than that by P450(11-beta)-2 [Morohashi et al., J. Biochem. 107 (1990) 635-640]. In this study, chimeric clones were constructed whose 6th, 36th and 82nd amino acid residues were exchanged with each other. Two original clones and six chimeric clones were expressed in COS-7 cells, and their steroidogenic activities studied. The ratio of aldosterone or 18-hydroxycorticosterone production to corticosterone production by one clone was compared with that of the other. The ratios for the four clones having Gly36 [P450(11-beta)-3 type] were 0.08-0.22, whereas those for the clones having Ser36 [P450(11-beta)-2 type] were 0.03-0.05, suggesting that the Gly36 structure is important for aldosterone production.