An unusual cysteine-containing histone H1-like protein and two protamine-like proteins are the major nuclear proteins of the sperm of the bivalve mollusc Macoma nasuta.
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.
Ausió
J
J
Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D006657:Histones / Q000302:isolation & purification*; D008297:Male; D008958:Models, Molecular; D008970:Molecular Weight; D008974:Mollusca; D009687:Nuclear Proteins / Q000302:isolation & purification*; D011479:Protamines / Q000302:isolation & purification*; D011487:Protein Conformation; D013094:Spermatozoa / Q000032:analysis*
D000596:Amino Acids; D006657:Histones; D009687:Nuclear Proteins; D011479:Protamines