Sperm-Specific Basic Proteins in the Holocephalan Fish Hydrolagus colliei (Chondrichthyes, Chimaeriformes) and...

Seven basic proteins can be isolated from sperm nuclei of the holocephalan ratfish Hydrolagus colliei. Two of these proteins (R3 and m0) are devoid of cysteine, whereas five of them (R1, R2, m1, m2, and m3) contain low levels of this amino acid residue. The proteins R1, R2, and R3 are major ones in the sperm nuclei of H. colliei, and they are analogous to basic proteins Z1, Z2, and Z3 (scylliorhinines) from the sperm of the elasmobranch Scyliorhinus canicula. However, taking into account the partial sequence of R3 protein and the number of cysteines in R1 and R2, these proteins do not seem to be homologous to the scylliorhinines. A comparison of sperm basic proteins between H. colliei (a holocephalan) and S. canicula (an elasmobranch) suggests a remarkable divergence of these proteins from a common ancestral pattern during the evolution of Chondrichthyes.