CLONING AND CHARACTERIZATION OF THE EPSILON-ISOFORM AND ZETA-ISOFORM OF THE 14-3-3-PROTEINS

Two prominent proteins (30 and 33 kD) in a purified preparation of the sheep pineal gland were studied. Amino acid analysis of tryptic pepti des indicated that the 33-kD protein was the epsilon isoform of the 14 -3-3 family of proteins, and that the 30-kD protein was the zeta- isof orm. The sheep pineal gland was found to have six other 14-3-3 isoform s in addition to the epsilon and zeta, suggesting that copurification of the epsilon and zeta forms may reflect the existence of home- or he terodimers comprised of these isoforms. To characterize 14-3-3 protein s further in the pineal gland, the full sequence of the epsilon isofor m and a partial sequence of the zeta isoform were cloned from a rat pi neal cDNA library and are reported here. Tissue distribution studies u sing Western blot analysis revealed that rat pineal and retina have le vels of 14-3-3 protein similar to those found in brain, and that relat ively low levels occur in other tissues. This investigation also revea led the E isoform was present at high levels in the rat pineal gland e arly in development and decreased steadily thereafter and that 30-kD i soforms exhibited the inverse developmental pattern.