Allurin, a 21-kDa sperm chemoattractant from Xenopus egg jelly, is related to mammalian sperm-binding proteins

Abstract

Previously, we demonstrated that a protein from Xenopus egg jelly exhibits sperm chemoattractant activity when assayed by either video microscopy or by sperm passage across a porous filter. Here we describe the isolation and purification of allurin, the protein responsible for this activity. Freshly oviposited jellied eggs were soaked in buffer, and the conditioned medium was loaded onto an anion exchange column and eluted with an NaCl gradient. The active fraction was purified further by RP-HPLC, the chemoattractant protein appearing as a single sharp peak. The amino acid sequence of the protein, determined by direct sequencing and cloning of cDNAs coding for the protein, consisted of 184 amino acids having a molecular mass of 21,073 Da. The protein shares homology with the mammalian cysteine-rich secretory protein (CRISP) family that includes testes-specific spermatocyte protein 1, a cell adhesion protein which links spermatocytes to Seritoli cells, and acidic epididymal glycoproteins that bind to sperm and have been implicated in sperm-egg fusion. Phylogenetic analysis suggests that allurin evolved from the ancestral protein that gave rise to the mammalian CRISP family. Addition of allurin to this family portends that the CRISP family represents a group of ''sperm escort'' proteins, which bind to sperm at various steps in their life history, facilitating passage from one functional stage to the next. Allurin stands out in this regard, representing both the first vertebrate sperm chemoattractant to be purified and sequenced and the first member of the CRISP family to be found in the female reproductive tract. sperm chemotaxis ͉ fertilization ͉ TPX-1 ͉ AEG ͉ CRISP

Cysteine‐rich secretory proteins are not exclusively expressed in the male reproductive tract

“…However, it is not without precedent. Allurin, which is a non-CRISP CAP, is produced by the oviductal secretory epithelium within Xenopus where it permeates the egg jelly and subsequently establishes a diffusion gradient and acts as a sperm chemoattractant (Olson et al, 2001;Xiang et al, 2004;Burnett et al, 2008). The mechanism through which allurin has a chemoattractant activity is currently unknown.…”

Identity and transfer of male reproductive gland proteins of the dengue vector mosquito, Aedes aegypti: Potential tools for control of female feeding and reproduction

“…AAEL009239 is a predicted CRISP. Proteins in this class are found in the seminal fluids of mammals (Cohen et al, 2001) and D. melanogaster (Mueller et al, 2004) and in the egg jelly of the frog, Xenopus laevis (Olson et al, 2001). A D. melanogaster CRISP (CG17575) participates in regulating the release of sperm from storage (Ravi Ram and Wolfner, In press).…”

“…In mammals, there is evidence suggesting that seminal fluid CRISPs are necessary for gamete fusion (Cohen et al, 2001). In Xenopus, a CRISP-like protein in the egg jelly acts as a sperm attractant (Olson et al, 2001). AAEL001121 and AAEL10596 are predicted lectins, a family of proteins which have been found to influence gamete interactions during fertilization (Romero et al, 1997) and regulate sperm binding to the female oviduct (Suarez et al, 1998) in mammals and mediate the release of sperm from female sperm storage organs in D. melanogaster (Ravi Ram and Wolfner, In press).…”

Sperm Chemotaxis: The First Authentication Events Between Conspecific Gametes Before Fertilization

“…Chemoattractants such as "resact " in sea urchins (Ward et al 1985 ;Guerrero et al 2010 ), "sepsap " in cuttlefi sh (Zatylny et al 2002 ), and "asterosap " in starfi sh (Böhmer et al 2005 ) are peptides. A 21-kDa protein named "allurin " in the amphibian Xenopus laevis (Olson et al 2001 ) and tryptophan in abalone (Riffell et al 2002 ) act as sperm chemoattractants. In the hydrozoan Hippopodius hippopus , the attractant has not yet been identifi ed but has been characterized as a small and thermoresistant protein with a molecular mass of 25 kDa and an isoelectric point of 3.5 (Cosson et al 1986 ).…”