Identification of multiple pregnancy-associated glycoproteins (PAGs) purified from the European bison (Eb; Bison bonasus L.) placentas

This paper describes the first identified chorionic PAGs in the European bison (Eb), named EbPAGs, predominantly expressed during early and mid-pregnancy (45–120 day post-coitum; dpc). Many EbPAGs were extracted from various cotyledonary tissues, precipitated, chromatographed (DEAE and VVA: Vicia villosa agglutinin), electrophoresed (1D- and 2D-PAGE), analysed by heterologous (cross-species) Western blotting and then micro-sequenced by Edman degradation. Finally, twelve selected VVA-purified isoforms (Ip 3.7–7.4) were entirely characterised. Nine identified NH2-terminal micro-sequences were found to be PAGs. On 45 dpc, three identified forms were named: EbPAG67A kDa (RGSNLTHPLRNIGDLFYVGN), EbPAG55B kDa (RGSNLTHPL) and EbPAG50C kDa (SQISLRGSNLTI). On 60 dpc, the next three forms were named: EbPAG71D kDa (RGSNLTIHPLRNIIDLFYVG), EbPAG55E kDa (RGSNLTHPLRNI) and EbPAG50F kDa (SQISLRGS). On 120 dpc, three other forms were named: EbPAG71G kDa (RGSNLTHPLRNIRDLFYVG), EbPAG60H kDa (RGSNLTTHPLRNIKDLVVYM) and EbPAG50I kDa (SGSNLTTV). These EbPAG (A–I) sequences are unique, as they are not identical to any other PAGs purified previously in related species of the Bovidae family. However, the EbPAGs (A–I forms) have some sequence resemblance to internal sequences of various full-length polypeptide PAG precursors (in silico translated from cloned cDNAs) identified in domestic cattle. Three other novel native isoforms (J1, J2 and K): EbUPG45 kDa J1 (SKDNYKNYIPLIVPFAT), EbUPG45 kDa J2 (SKDNQKNYIPLIVPFAT) and EbUPG76 kDa K (SPEFTV), were temporarily named ‘unknown placental glycoproteins’ (UPGs), due to their efficient VVA-purification (specific for glycoproteins only) and a lack of considerable consensus to previously sequenced placental glycoproteins in the Bovidae family. This is the first study identifying NH2-terminals of multiple/diverse EbPAGs and some EbUPGs purified from the synepitheliochorial cotyledonary placenta of the endangered Bison bonasus (Red List).