Abstract
The sperm-specific protamine-like (PL) components PL-I, PL-II, and PL-III from the sperm of the bent-nose clam Macoma nasuta have been isolated and characterized for the first time. These proteins coexist in the sperm nuclei with a small percentage of a full histone complement. All of them have a very similar amino acid composition, following what seems to be the general composition prototype for the class Bivalvia (Ausió, J. (1986) Comp. Biochem. Physiol. B Comp. Biochem. 85, 439-449). Nevertheless, they have different molecular weights (PL-I = 23,500, PL-II = 15,600, and PL-III = 7,900) as measured by sedimentation equilibrium in the analytical ultracentrifuge. Furthermore, the PL-I component shares common features with the proteins of the histone H1 family. Yet, it is very unusual, for it contains 2 cysteine residues that are located in the trypsin-resistant core of this protein. The protamine-like fraction PL-III exhibits intraspecific microheterogeneity which is reflected by the presence of two protein variants which most probably are the result of an allelic polymorphism.
Highlights
The sperm-specific protamine-like (PL) components PL-I, PL-11, and PL-I11 from the sperm of the bentnose clam Macoma nasuta have been isolated and characterized for the first time
It is not easy to conceive the role of this latter protein in the higher order organization of the nucleoprotein complex, especially in the presence of a very low amount of the canonical core histones (H2A, H2B, H3, and H4).The analysis presented here represents the necessary basis for further studies in that direction, which in turn may help us to understand moreclosely the detailed molecular features underlying the high versatility of this histone H1 family in accomplishing their commonrole inchromatin condensation
The chromatin of the sperm of M . nasuta is organized by three major protamine-like (PL)l proteins, PL-I,PL-11,and PL-I11(Ausib,1986).In the present paper I have found that one of them, PL-I, is more closely related to histones than toprotamines,this protein component has a strong similarity to the proteins of the histone H1 family, as has been found for the com
Summary
The samples of the bent-nose clam M. nasuta were collected in Coos Bay, OR, and the sperm was collected as described elsewhere (Ausi6, 1986). HPLC Chromatographx-HPLC chromatography was conducted on a (25 X 0.46 cm) 300-A CI8Vydac column at 0.75 ml/min in the presence of 0.1% trifluoroacetic acid using an acetonitrile gradient. Acetic AcidlUrea Gels-High resolution polyacrylamide gels (acrylamide/bisacrylamide, 301) containing acetic acid and 2.5 M urea were routinely prepared as described elsewhere (Ausi[6] et al, 1986). Two-dimensional Electrophoresis-Two-dimensional electrophoresis combining the above techniques was performed as described elsewhere (Ausi6, 1986). Silver staining of these gels was carried out according to Oakley et al (1980). Amino acid analysis were carried out by the phenylisothiocyanate method in an IBM-LC9533 equipped with an IBM 9000 controller and anIBM C-18 column as described elsewhere (Ausi6, 1986)
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