Nuclear basic protein transition during sperm differentiation. Amino acid sequence of a spermatid-specific protein from the dog-fish Scylliorhinus caniculus |
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Authors: | M Chauvière A Martinage G Briand P Sautière P Chevaillier |
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Institution: | Laboratoire de Biologie Cellulaire, Université Paris-Val de Marne, Créteil, France. |
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Abstract: | During dog-fish spermatogenesis, chromatin undergoes a continuous processing which involves two basic protein transitions: the first from somatic-type histones to spermatid-specific proteins and the second leading to protamines. Two spermatid-specific proteins S1 and S2 were isolated from nuclei of spermatid-enriched testis zone and the amino acid sequence of S1 has been determined. S1 contains 87 amino acids and has a molecular mass of 11179 Da. It is mainly characterized by a high content of basic residues (45%) and the presence of one residue of cysteine. Its primary structure shows that the N-terminal half is highly basic while the hydrophobic residues are preferentially localized in the C-terminal region. Three forms of S1 are present in testis which correspond to di-, mono- and nonphosphorylated molecules. This spermatid-specific protein shares no common structural feature with either histones and dog-fish protamines or rat spermatid-specific protein which has been previously described. |
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