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An antigenically related polypeptide family is a major structural constituent of a stable acrosomal matrix assembly in bovine spermatozoa
Ist Teil von
Biology of reproduction, 1997-08, Vol.57 (2), p.325-334
Ort / Verlag
Madison, WI: Society for the Study of Reproduction
Erscheinungsjahr
1997
Quelle
MEDLINE
Beschreibungen/Notizen
The apical and principal segments of the bovine acrosome contain a stable matrix complex that is bound to the outer acrosomal
membrane and exhibits hydrolase-binding activity. The present study was undertaken to determine whether the outer acrosomal
membrane-associated matrix complex (OMC) is composed of a unique set of acrosomal proteins and to define its fate during both
capacitation and the acrosome reaction. A purified OMC fraction was isolated from ejaculated spermatozoa, and one polypeptide
of 32 kDa (OMC32) was purified to homogeneity and used for N-terminal sequence analysis and preparation of monospecific antisera.
Immunofluorescence staining of sperm with anti-OMC32 demonstrated that the polypeptide localized specifically to the apical
and principal segments of the acrosome. Immunoelectron microscopy further revealed that OMC32 was restricted to the stable
matrix assembly and was not associated with the inner acrosomal membrane or the equatorial segment. Immunoblot analyses of
sperm lysates and of the purified OMC fraction revealed that anti-OMC32 recognized an antigenically related family of polypeptides
between 38 and 19 kDa. These polypeptides exhibited no size processing during capacitation or the acrosome reaction, and they
were not released during the acrosome reaction but remained in the particulate cell subfraction, associated with the hybrid
membrane complex. N-terminal sequence analysis of OMC32 indicated a structural relationship to the SP-10 polypeptide family
of human and baboon spermatozoa. The potential function of the OMC complex and differences in the intraacrosomal distribution
of bovine OMC32-related polypeptides from that reported for acrosomal SP-10 polypeptides in other species are discussed.