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In this work, we show by several methods that the Eledone cirrhosa sperm is a cell very rich in cysteine. A high proportion of these cysteine residues is found linked by disulphide bonds (-cys-S-S-cys-), conferring a remarkable chemical stability to the nucleus and outer dense fibers. We have paid special attention to purifying and analyzing the protein content of sperm nuclei and comparing it with other E. cirrhosa sperm proteins and with Octopus sp protamine. Contrary to the previous results of Subirana et al. (1973. Biochim Biophys Acta 317:364–379), we find that E. cirrhosa sperm nuclei contain only one major protein, a protamine. This sperm nuclear basic protein is a very cysteine-rich molecule and is different from known cephalopod protamines. Consequently, sperm cells of E. cirrhosa display a general “keratinous” state that includes their nucleus. We discuss how this fact may be related to some peculiar reproductive behavioral characteristics of this species. J. Exp. Zool. 283:580–589, 1999.
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Gimenez‐Bonafé et al. (1999) studied this question.
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