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DNA Cell Biol. 2012 Aug;31(8):1392-402. doi: 10.1089/dna.2011.1547. Epub 2012 Apr 26.

A sperm nuclear basic protein from the sperm of the marine worm Chaetopterus variopedatus with sequence similarity to the arginine-rich C-termini of chordate protamine-likes.

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Department of Structural and Functional Biology, University of Naples Federico II, Napoli, Italy.


The sperm nuclear basic proteins (SNBPs) of the marine annelid worm Chaetopterus variopedatus have been shown previously to consist of a mixture of two SNBPs: histone H1-like (CvH1) and C.variopedatus protamine-like (CvPL). Here, we report the structural characterization of CvPL. The protein has a molecular weight of 8370.5 Da, a K/R ratio of 0.34, and a secondary structure, which are intermediate between those of protamine (P) and protamine-like (PL) SNBPs. The N-terminal sequence of CvPL shows a high extent of similarity with the arginine-rich C-terminal domain of chordate PL-type SNBPs. Furthermore, the protein binds to DNA in a similar fashion as vertebrate PLs and their own CvH1, but in a way that is different from that of the lysine-rich somatic H1 histones. We have experimentally determined the molar ratio CvH1:CvPL to be ∼1:6 in C. variopedatus sperm. Based on all of these, a model is proposed for the organization of the sperm chromatin by CvH1 and CvPL.

[Indexed for MEDLINE]

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