Comparison of the 95,000 molecular weight protein from Limulus sperm with muscle alpha-actinin

The 95,000 molecular weight protein (95K protein) of the false discharges of Limulus sperm, purified by means of preparative gel electrophoresis in the presence of sodium dodecyl sulfate, was compared with a 95K protein from Limulus muscle and chicken gizzard alpha-actinin. The results were as follows. 1) One-dimensional peptide mapping using four different proteases showed differences among these proteins. 2) Two-dimensional peptide mapping using trypsin showed that about 30% of the peptides in the digest of the sperm 95K protein were similar to those of chicken gizzard alpha-actinin and about 50% of the peptides were similar to those of the Limulus muscle 95K protein. 3) The sperm 95K protein contained relatively large amounts of Gly, Pro, and Ser and relatively small amounts of Glu and Leu compared to the muscle proteins. 4) Antibodies against the sperm 95K protein did not cross-react with the Limulus muscle 95K protein or chicken gizzard alpha-actinin. These results suggest that the 95K protein of sperm is different from alpha-actinin in primary structure.