CONFORMATION OF NUCLEOPLASMIN AND ITS INTERACTION WITH DNA-PROTAMINE COMPLEX AS A SIMPLE-MODEL OF FISH SPERM NUCLEI

Nucleoplasmin was isolated from Xenopus laevis eggs and purified by an improved method using an open column. Its conformation was investigat ed spectrophotometrically by UV, CD and fluorescence. It was shown tha t alpha-helix content of nucleoplasmin was 30-40%, and one of the two tryptophan residues in nucleoplasmin located in the hydrophobic surrou ndings and the other in the relatively hydrophilic surroundings. The i solated nucleoplasmin was found to decondense sperm nuclei of salmon a lso, suggesting a possibility of the existence of nucleoplasmin-like p rotein in fish as well. Collapse of the protamine (salmine)-DNA comple x as a simple model for fish sperm nuclei by nucleoplasmin was directl y observed by measuring OD320 of aqueous protamine-DNA mixtures. This is a molecular level observation for the removal of protamine from DNA -protamine complex. (C) 1997 Elsevier Science B.V.