Polyamine-peptide conjugates: proposed functions.

Six polyamine-conjugated proteins were identified in human amniotic fluid. Three contained covalently bound spermine, one contained covalently bound spermidine, and two contained covalently bound putrescine. All were characterized by high content of serine, glycine, glutamate, and aspartate. Polyamination of proteins may participate in mechanisms for (1) polyamine specificity in cell growth; (2) cell surface attachment of polyamines; (3) transport of polyamines; (4) endocytosis and other cellular uptake processes; and (5) signaling protein degradation.