Protamine polymorphism in Xenopus laevis laevis.

Protamines from individual frogs of the subspecies Xenopus laevis laevis were compared by electrophoresis on polyacrylamide gels containing acetic acid, urea, and Triton X-100 to determine if the expression of protamine genes differs among individuals. Two electrophoretic bands, SP2a and SP2b, appeared to be expressed as allelic variants. Of 33 frogs, 19 expressed only SP2a, 11 expressed both SP2a and SP2b, and three expressed only SP2b. Electrophoretic analysis of partial V8 protease digests could not distinguish the peptides released from SP2a and SP2b. Differences in sperm development between individuals were not detected by light or electron microscopy. The results suggest that protamine polymorphism can exist among individuals of a species without an apparent effect on sperm development or sperm function.