Sperm basic proteins in the turtle Chrysemys picta: Characterization and evolutionary implications

Abstract

AbstractBasic proteins in the sperm nuclei of reptiles have been classified cytochemically as type 3 intermediate proteins (Kasinsky et al., '87) or electrophoretically as type 1 protamines (Elsevier and Pieau, '88) according to Bloch's ('69) classification scheme. In this paper we have purified the sperm basic proteins of the painted turtle Chrysemys picta and show that they display considerable microheterogeneity, like the protamines of some fishes and other vertebrates. In addition, the amino acid composition of C. picta sperm basic proteins is very similar to that of protamines in birds (Chiva et al., '87), although those of the turtle lack tyrosine and contain low amounts of lysine and histidine. These facts allow us to relate reptilian sperm basic proteins to the main evolutionary line of vertebrate protamines and to discuss possible mechanisms for the macroevolutionary trend of relative constancy of sperm basic proteins in reptiles, birds, and mammals.