CHAPTER 17
Structural Characterisation of Porcine Seminal Plasma
Psp-I/Psp-II, a Paradigm Spermadhesin Molecule Built
by Heterodimerization of Glycosylated Subunits
J. J. CALVETE i and L. SANZ i
1
Introduction:
Lectin-Carbohydrate Binding Mechanism in Mammalian Fertilisation
The mechanism of initial binding between mammalian gametes involves recognition of glycan moieties attached to glycoprotein components of the egg acellular
coat, the zona pellucida, by carbohydrate-binding proteins (lectins) on the surface of acrosome-intact, capacitated spermatozoa (reviewed by Benoff 1997,
Sinowatz et al. 1997; Tulsiani et al. 1997; Topfer-Petersen et al. 1998). A considerable number of molecules have been proposed to participate in this complementary, carbohydrate-based binding process in the six mammalian species (mouse,
rat, boar, guinea pig, rabbit, and human) most thoroughly investigated by different laboratories using diverse techniques, like
(i) incubation of Western blots of sperm proteins with labelled zona pellucida
glycoproteins or specific poly- and monoclonal antibodies which inhibit
sperm-zona pellucida binding;
(ii) affinity chromatography of detergent-extracted sperm proteins on immobilised zona pellucida glycoproteins;
(iii) cross-linking of sperm surface proteins to zona pellucida ligands; and
(iv) correlation with infertility.
On the other hand, mammalian zonae pellucidae have conserved structure and
simple protein composition. They typically consist of only 3 glycoproteins,
encoded by three different genes termed ZPA, ZPB, and ZPC, arranged into a
loose 2-25 f.tm thick meshwork which encases the oocyte. However, zona pellucida glycoproteins display species-specific glycosylation patterns which contribute to the non-conserved sperm receptor activity among species (Green 1997).
The large diversity of both the structure of glycans of zona pellucida glycoproteins and the receptor molecules on spermatozoa, strongly suggests that several
glycan-lectin recognition events may be involved before productive gamete interaction can occur. Noteworthy, little is known about the hierarchy of interactions
and the cross-talking between different receptor/ligand systems, which may collectively dictate the species-specificity of gamete interaction. Thus, although the
lInstituto de Biomedicina de Valencia, C.S.I.e., Jaime Roig 11, E-4601O Valencia, Spain; Phone,
+34 963391775; Fax, +34 963690800; e-mail: jcalvete@ibv.csic.es.
Structural Characterisation of Porcine Seminal Plasma
Psp-I/Psp-II, a Paradigm Spermadhesin Molecule Built
by Heterodimerization of Glycosylated Subunits
J. J. CALVETE i and L. SANZ i
1
Introduction:
Lectin-Carbohydrate Binding Mechanism in Mammalian Fertilisation
The mechanism of initial binding between mammalian gametes involves recognition of glycan moieties attached to glycoprotein components of the egg acellular
coat, the zona pellucida, by carbohydrate-binding proteins (lectins) on the surface of acrosome-intact, capacitated spermatozoa (reviewed by Benoff 1997,
Sinowatz et al. 1997; Tulsiani et al. 1997; Topfer-Petersen et al. 1998). A considerable number of molecules have been proposed to participate in this complementary, carbohydrate-based binding process in the six mammalian species (mouse,
rat, boar, guinea pig, rabbit, and human) most thoroughly investigated by different laboratories using diverse techniques, like
(i) incubation of Western blots of sperm proteins with labelled zona pellucida
glycoproteins or specific poly- and monoclonal antibodies which inhibit
sperm-zona pellucida binding;
(ii) affinity chromatography of detergent-extracted sperm proteins on immobilised zona pellucida glycoproteins;
(iii) cross-linking of sperm surface proteins to zona pellucida ligands; and
(iv) correlation with infertility.
On the other hand, mammalian zonae pellucidae have conserved structure and
simple protein composition. They typically consist of only 3 glycoproteins,
encoded by three different genes termed ZPA, ZPB, and ZPC, arranged into a
loose 2-25 f.tm thick meshwork which encases the oocyte. However, zona pellucida glycoproteins display species-specific glycosylation patterns which contribute to the non-conserved sperm receptor activity among species (Green 1997).
The large diversity of both the structure of glycans of zona pellucida glycoproteins and the receptor molecules on spermatozoa, strongly suggests that several
glycan-lectin recognition events may be involved before productive gamete interaction can occur. Noteworthy, little is known about the hierarchy of interactions
and the cross-talking between different receptor/ligand systems, which may collectively dictate the species-specificity of gamete interaction. Thus, although the
lInstituto de Biomedicina de Valencia, C.S.I.e., Jaime Roig 11, E-4601O Valencia, Spain; Phone,
+34 963391775; Fax, +34 963690800; e-mail: jcalvete@ibv.csic.es.