Lectin binding to guinea-pig sperm zipper particles

Zipper particles are morphologically distinct transmembrane specializations of sperm tails. In freeze-fracture replicas of the guinea-pig sperm, they appear as an interdigitating double row of intramembranous particles running longitudinally within the plasma membrane of the principal piece. In thin section, zipper particles appear as an increase in electron density both above and below the bilayer. Zipper particles have been observed on a variety of both mammalian and non-mammalian species, suggesting that they have been conserved to serve an essential sperm function. As a first step towards biochemically characterizing guinea-pig zipper particles and towards developing a zipper isolation procedure, we performed an in situ lectin-binding study. Examination of nine gold- or ferritin-conjugated lectins revealed that three lectins, concanavalin A, Ricinus communis agglutinin I and wheatgerm agglutinin, bound to zipper particles. These lectin binding results suggest the presence of N-linked oligosaccharides within zipper particles. The results of the lectin binding study were then used in conjunction with a detergent solubilization procedure to identify potential zipper components. Detergent solubilization involved two non-ionic detergents: digitonin, which solubilized most of the plasma membrane, but left approximately two thirds of the zipper particles attached to the cytoskeleton, and Triton X-100, which solubilized the remaining zipper particles while leaving most other sperm structures intact. Within sodium dodecyl sulphate/polyacrylamide gels of the Triton-X-100-soluble fraction potential zipper particle components with the same lectin-binding characteristics as in situ zipper particles were identified.