LYSINE-87 IS A FUNCTIONALLY IMPORTANT RESIDUE IN HUMAN PROTHYMOSIN-ALPHA

Human prothymosin alpha mutants were generated with the aid of random mutagenesis and screened for their ability to inhibit yeast Saccharomy ces cerevisiae cell growth. Conversion of Lys-87 to Glu resulted in an inactivated prothymosin alpha mutant, which lost the ability of the m ild-type protein to block yeast cell growth, We propose that prothymos in alpha may possess a bipartite rather than monopartite nuclear local ization signal, which includes Lys-87, and that the above mutation des troys one part of the nuclear localization signal, thus preventing eff icient nuclear uptake of prothymosin alpha.