Cloning and Characterization of the ∈ and ζ Isoforms 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 peptides indicated that the 33-kD protein was the ∈ isoform of the 14-3-3 family of proteins, and that the 30-kD protein was the ζ isoform. The sheep pineal gland was found to have six other 14-3-3 isoforms in addition to the ∈ and ζ, suggesting that copurification of the ∈ and ζ forms may reflect the existence of homo- or heterodimers comprised of these isoforms. To characterize 14-3-3 proteins further in the pineal gland, the full sequence of the ∈ isoform and a partial sequence of the ζ isoform were cloned from a rat pineal cDNA library and are reported here. Tissue distribution studies using Western blot analysis revealed that rat pineal and retina have levels of 14-3-3 protein similar to those found in brain, and that relatively low levels occur in other tissues. This investigation also revealed the ∈ isoform was present at high levels in the rat pineal gland early in development and decreased steadily thereafter and that 30-kD isoforms exhibited the inverse developmental pattern.