Chemical Synthesis of Partially and Fully Phosphorylated Protamines

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Abstract
Chromatographically purified components Z and YI of clupeine from herring have been phosphorylated by a chemical method. To enhance solubility in trimethylphosphate, the protamine capronate salts were used and phosphorylation was performed with POCl3. Both serine and threonine residues were phosphorylated; however, besides monophosphate esters considerable amounts of polyphosphate esters were obtained. Its nature was identified by 31P nuclear magnetic resonance spectroscopy and by chemical methods, such as comparison of the hydrolysis rate with that of ADP and phoshocreatine, respectively. The pyrophosphate bonds were cleaved by controlled hydrolysis with HCl. The phosphorylated protamine species were purified by gel filtration and chromatography on a Sephadex CM column. Fully phosphorylated clupeine Z (3 serine residues and 3 phosphates) and YI (3 serine, 2 threonine residues and 5 phosphates) were obtained as well as partially phosphorylated fractions; in the case of clupeine Z the resolution into mono, doubly and triply (fully) phosphorylated fractions was excellent. The overall yield of phosphorylated clupeine was better than 50%.