Nuclear-accumulation kinetics of p9(CksHs1) and p9(CksHs2) in live plant cells correlate with immunochemical characteristics

The two human homologues of the fission yeast cell cycle protein p13(suc1) displayed structural characteristics consistent with their existing in solu tion as differently folded monomers despite 81% identity with respect to th eir primary structures and both being capable of fulfilling the functions o f their homologues in fission and budding yeasts. Carboxyfluorescein-labell ed p9(CksHs1) and p9(CksHs2) retained their native structures. When microin jected into live stamen hair cells of Tradescantia virginiana, the labelled proteins accumulated in the nuclei of the cells. Markedly different nuclea r-accumulation kinetics indicated that the human proteins interact differen tly with other cellular constituents, which supports the proposition that t hey may have different roles in cellular regulation.