CHICK KIDNEY FERREDOXIN - COMPLEMENTARY-DNA CLONING AND VITAMIN-D EFFECTS ON MESSENGER-RNA LEVELS

Vertebrate ferredoxin is non-heme iron-sulfur protein found in steroid ogenic tissues that serves as an electron shuttle in mitochondrial mix ed function oxidase systems such as the 25-hydroxyvitamin D-3-1 alpha- hydroxylase. A 2530-bp chick kidney ferredoxin cDNA was cloned, and th e association between ferredoxin mRNA levels and the regulation of 1 a lpha-hydroxylase activity by vitamin D status was examined. The cDNA s equence indicates that the chick kidney mitochondrial mixed function o xidases uses the same ferredoxin as do those in the chick testis and t hat the chick ferredoxin shares greater than 92% amino acid homology w ith mammalian ferredoxins. Southern blot analysis of genomic DNA indic ates that there is a single copy of the ferredoxin gene present in the chick genome. Three species of mRNA, 1.8, 3.5 and 5.5 kb, were identi fied by Northern analysis. Slot blot analysis of poly A+ RNA from kidn eys of vitamin D-deficient or -replete chicks indicates a 40% inductio n of ferredoxin message levels in the vitamin D-deficient chick kidney . This suggests that gene regulation of ferredoxin may be part of the mechanism of regulation for 25-hydroxyvitamin D-3-1 alpha-hydroxylase activity in the chick kidney.