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At least 19 recordsLinked to original sources
PubMed2002

Receptor-ligand interaction between vitellogenin receptor (VtgR) and vitellogenin (Vtg), implications on low density lipoprotein receptor and apolipoprotein B/E. The first three ligand-binding repeats of VtgR interact with the amino-terminal region of Vtg.

The vitellogenin receptor (VtgR) belongs to the low density lipoprotein receptor (LDLR) gene family. It mediates the uptake of vitellogenin (Vtg) in oocyte development of oviparous animals. In this study, we cloned and characterized two forms of Oreochromis aureus VtgR. Northern analysis showed that VtgR was specifically expressed in ovarian tissues. However, reverse transcription-PCR indicates that either there are trace levels of expression of VtgR or a homolog of LDLR exists in nonovarian tissues. The VtgR is highly homologous to the very low density lipoprotein receptor. To better understand the mechanism by which similar structural modules in the ligand-binding domain bind different ligands, we used the yeast two-hybrid system to screen for the minimal interaction motifs in Vtg and VtgR. The amino-terminal region of the lipovitellin I domain of Vtg interacts with the ligand-binding domain of VtgR. The first three ligand-binding repeats of the receptor were found to be essential for ligand binding. Computational analysis of the binding sequence indicates that Vtg has a similar receptor-binding region to apolipoprotein (apo) E and apoB. Site-directed mutagenesis of this region indicates electrostatic interaction between Vtg and its receptor. Sequence analysis suggests the coevolution of receptor-ligand pairs for the LDLR/apo superfamily and suggests that the mode of binding of LDLR/very low density lipoprotein receptor to apoB and apoE is inherited from the electrostatic attraction of VtgR and Vtg.

Amino Acid Sequence↗
PubMed2001

Organization and developmental expression of the mosquito vitellogenin receptor gene.

Vitellogenin is a precursor of the major yolk protein, vitellin. It is internalized by developing oocytes via receptor-mediated endocytosis. Previously, we characterized the vitellogenin receptor (VgR) from oocytes of the mosquito Aedes aegypti [Sappington, T.W., Kokoza,V.A., Cho,W.L. and Raikhel,A.S. (1996) Molecular characterization of the mosquito vitellogenin receptor reveals unexpected high homology to the Drosophila yolk protein receptor. Proc Natl Acad Sci USA 93: 8934-8939]. The VgR receptor has a unique structure with two putative ligand-binding domains. In order to understand the regulation of this important molecule, we characterized the VgR gene structure and its expression during vitellogenesis in the mosquito A. aegypti. We report here that the VgR gene was separated by five introns that have an average length of 60 bp, except for the second intron which was more than 20 kb long. Most introns were located within the coding regions of the first protein domain. We isolated two allelic variations of the VgR gene, VgR1 and VgR2, the nucleotide sequences of which differing only in their 5'-flanking regions. Considering their frequency in the mosquito genome, VgR2 appeared to be a major allele. The expression of VgR mRNA was studied by the Northern blot analysis and in situ hybridization. The level of the VgR transcript started to rise in the ovary one day post-eclosion. It continued its dramatic rise during the vitellogenic period, reaching its peak at 24 h PBM. The VgR transcript was present exclusively in ovaries where it was seen in oocytes and nurse cells of primary follicles and germ-line cells of the germarium.

Aedes↗
PubMed1995

The Drosophila yolkless gene encodes a vitellogenin receptor belonging to the low density lipoprotein receptor superfamily.

Sequence comparisons of vitellogenins from a wide range of organisms have identified regions of similarity not only to each other but also to vertebrate apolipoproteins (e.g. apoB-100 and apoE). Furthermore, the chicken vitellogenin receptor, which also binds apolipoproteins receptor (LDLR) superfamily [Bujo, H., Hermann, M., Kaderli, M. O., Jacobsen, L., Sugawara, S., Nimpf, J., Yamamoto, T. & Schneider, W. J. (1994) EMBO J. 13, 5165-5175]. The yolk proteins of higher dipterans are exceptional, however, and instead show similarity to lipoprotein lipases. The molecular characterization of the putative Drosophila melanogaster vitellogenin receptor gene, yolkless (yl), described in this report reveals that the protein it encodes (Yl), is also a member of the LDLR superfamily. The ovary-specific 6.5-kb yl RNA codes for a protein of approximately 210 kDa which contains all three motifs common to the LDLR class of proteins. Within this superfamily, Yl may be related more to the LDLR-related proteins (LRPs), which bind both apolipoproteins and lipoprotein lipases. The similarity of Yl to the other LDLR proteins is restricted to the putative extracellular domain. Most noticeably, the cytoplasmic domain of Yl lacks the typical NPXY sequence which is involved in receptor internalization.

Amino Acid Sequence↗
PubMed2005

Molecular cloning, characterization and regulation of the cockroach vitellogenin receptor during oogenesis.

The vitellogenin receptor (VgR) belongs to the low density lipoprotein receptor (LDLR) superfamily, and mediates the uptake of vitellogenin (Vg) into developing oocytes of all oviparous species. We cloned and characterized a VgR from previtellogenic ovaries of the cockroach, Periplaneta americana (Pa). This is the first report on a VgR from a hemimetabolous insect. The cDNA, comprising 5722 bp, encoded a 1790-residue mature protein with a predicted molecular mass of 200.5 kDa. We next characterized the ovarian expression pattern, developmental regulation and cellular distribution of the VgR mRNA and protein. Northern blot analysis confirmed that a approximately 7.2 kb transcript was specifically expressed in ovarian tissues at high levels throughout ovarian development, especially in previtellogenic ovaries and in ovaries before adult emergence. RNA in situ hybridization and immunocytochemistry localized the VgR mRNA and protein to germ-line derived cells, the oocytes, and revealed that VgR gene transcription and translation begin very early during oocyte differentiation in the germarium. Immunoblot analysis detected an ovary-specific VgR protein of approximately 210 kDa that was present in previtellogenic ovaries on the day of female emergence. The VgR protein signal strengthened every day and was intense after initiation of vitellogenesis and onset of Vg uptake. The immunoblotting of vitellins demonstrated that Vg uptake occurred on day 5, one day after Vg first appeared in the haemolymph, indicating that the receptor-endocytotic machinery starts functioning soon after the ligand becomes available.

Amino Acid Sequence↗
PubMed1996

Molecular characterization of the mosquito vitellogenin receptor reveals unexpected high homology to the Drosophila yolk protein receptor.

The mosquito (Aedes aegypti) vitellogenin receptor (AaVgR) is a large membrane-bound protein (214 kDa when linearized) that mediates internalization of vitellogenin, the major yolk-protein precursor, by oocytes during egg development. We have cloned and sequenced two cDNA fragments encompassing the entire coding region of AaVgR mRNA, to our knowledge the first insect VgR sequence to be reported. The 7.3-kb AaVgR mRNA is present only in female germ-line cells and is abundant in previtellogenic oocytes, suggesting that the AaVgR gene is expressed early in oocyte differentiation. The deduced amino acid sequence predicts a 202.7-kDa protein before posttranslational processing. The AaVgR is a member of the low density lipoprotein receptor superfamily, sharing significant homology with the chicken (Gallus gallus) VgR and particularly the Drosophila melanogaster yolk protein receptor, in spite of a very different ligand for the latter. Distance-based phylogenetic analyses suggest that the insect VgR/yolk protein receptor lineage and the vertebrate VgR/low density lipoprotein receptor lineage diverged before the bifurcation of nematode and deuterostome lines.

Aedes↗
PubMed1995

Mosquito vitellogenin receptor: purification, developmental and biochemical characterization.

Vitellogenin receptors (VgRs) play a critical role in egg development of oviparous animals by mediating endocytosis of the major yolk protein precursor, vitellogenin. A modification of the method for extracting the mosquito (Aedes aegypti) VgR from ovary membranes resulted in an 11-fold higher yield and 56-fold increase in relative purity of the VgR, in turn permitting purification, antibody production, and microsequencing. A Kd of 15 nM was estimated from binding assays for the enriched VgR, indicating a very high affinity for its ligand. Immunoprecipitation of [14C]VgR using anti-VgR polyclonal antibodies followed by SDS-PAGE under reducing conditions and fluorography demonstrated that the 205 kDa VgR does not consist of subunits held together with disulfide bonds. However, an immunoblot of the native VgR suggests that it exists as an approximately 390 kDa noncovalent homodimer in its native state. Immunoblot assays confirmed that the VgR is present only in ovarian tissue. A quantitative immunoassay of VgR extracts showed that VgR was present in previtellogenic ovaries on the day of emergence, increasing from 2 ng to more than 10 ng per ovary by day 5. After initiation of vitellogenesis and onset of Vg uptake, VgR quantity increased rapidly between 8 and 24 h after a blood meal, then began to decline between 24 and 36 h. Immunocytochemistry confirmed the presence of substantial amounts of the VgR in 4-day-old previtellogenic oocytes. In both previtellogenic and vitellogenic ovaries, the VgR was present only in the oocyte, primarily in the cortex.

Aedes↗
PubMed2002

Receptor mediated yolk protein uptake in the crab Scylla serrata: crustacean vitellogenin receptor recognizes related mammalian serum lipoproteins.

The receptor-mediated uptake of major yolk protein precursor, vitellogenin (Vg) is crucial for oocyte growth in egg laying animals. In the present study plasma membrane receptor for Vg was isolated from the oocyte of the red mud crab, Scylla serrata. Vitellogenin receptor (VgR) protein was visualized by ligand blotting using labeled crab Vg ((125)I-Vg) as well as labeled low density lipoprotein ((125)I -LDL) and very low density lipoprotein ((125)I-VLDL) isolated from rat. The endocytosis of Vg was visualized in the crab oocyte by ultrastructural immunolocalization of Vg. The Vg receptor was purified by gel filtration high performance liquid chromatography (HPLC) and its molecular weight was estimated to be 230 kDa. In direct binding studies, the receptor exhibited high affinity (dissociation constant K(d) 0.8x10(minus sign6) M) for crab Vg. Vitellogenin receptor was observed to have an increased affinity to crab Vg in the presence of Ca(2+) and the binding was inhibited by suramin, suggesting similarities between crab VgR and low density lipoprotein receptor (LDLR) superfamily of receptor protein. Furthermore, the crab VgR showed significant binding ability to mammalian atherogenic lipoproteins such as LDL and VLDL. This suggests that there is a tight conservation of receptor binding sites between invertebrate (crab) Vg and vertebrate (rat) LDL and VLDL.

Animals↗
PubMed1987

Receptor-mediated endocytosis in Xenopus oocytes. I. Characterization of the vitellogenin receptor system.

We have investigated the vitellogenin (VTG) receptor system in Xenopus oocytes since these cells are specialized for endocytosis. Oocytes have between 0.2 and 3 X 10(11) receptors per 1-mm cell. There is only a single class of receptors of low affinity (1.3 X 10(-6) M at 22 degrees C and 2-4 X 10(-6) M at 0 degree C), but high specificity (less than 5% nonspecific binding at 2 X 10(-6) M). The specific internalization rate of the VTG receptor (around 2 X 10(-3) s-1) is first order, highly variable, and at the upper end of the range of values reported for mammalian cells. The receptor association rate constant (9.6 X 10(2) M-1 s-1) is extremely low although the dissociation rate constant was immeasurable. Calcium is required for VTG binding, and low pH does not dissociate the VTG-receptor complex. Monensin treatment at 100 microM caused the loss of surface receptors with a t1/2 of 3 h and the accumulation of internalized ligand in a "pre-lysosomal" endocytic compartment. Conversely, the recovery of surface VTG receptors that were removed with trypsin occurred with a t1/2 of about 2 h. These observations indicate that oocytes have very large intracellular pools of receptors and that although surface receptors are internalized on the time scale of minutes, the intracellular pool is recycled on the time scale of hours.

Animals↗
PubMed2000

Regulation of the vitellogenin receptor during Drosophila melanogaster oogenesis.

In many insects, development of the oocyte arrests temporarily just before vitellogenesis, the period when vitellogenins (yolk proteins) accumulate in the oocyte. Following hormonal and environmental cues, development of the oocyte resumes, and endocytosis of vitellogenins begins. An essential component of yolk uptake is the vitellogenin receptor. In this report, we describe the ovarian expression pattern and subcellular localization of the mRNA and protein encoded by the Drosophila melanogaster vitellogenin receptor gene yolkless (yl). yl RNA and protein are both expressed very early during the development of the oocyte, long before vitellogenesis begins. RNA in situ hybridization and lacZ reporter analyses show that yl RNA is synthesized by the germ line nurse cells and then transported to the oocyte. Yl protein is evenly distributed throughout the oocyte during the previtellogenic stages of oogenesis, demonstrating that the failure to take up yolk in these early stage oocyte is not due to the absence of the receptor. The transition to the vitellogenic stages is marked by the accumulation of yolk via clathrin-coated vesicles. After this transition, yolk protein receptor levels increase markedly at the cortex of the egg. Consistent with its role in yolk uptake, immunogold labeling of the receptor reveals Yl in endocytic structures at the cortex of wild-type vitellogenic oocytes. In addition, shortly after the inception of yolk uptake, we find multivesicular bodies where the yolk and receptor are distinctly partitioned. By the end of vitellogenesis, the receptor localizes predominantly to the cortex of the oocyte. However, during oogenesis in yl mutants that express full-length protein yet fail to incorporate yolk proteins, the receptor remains evenly distributed throughout the oocyte.

Animals↗
PubMed1996

Vitellogenin receptors during vitellogenesis in the rainbow trout Oncorhynchus mykiss.

Rainbow trout vitellogenin receptors have been characterized by ligand blotting and Scatchard analysis. Their evolution has been studied over a reproductive cycle in a broodstock of 2-year-old females. The receptors were prepared from ovarian membrane homogenates and were solubilized using n-octyl-beta-D-glucopyranoside. The visualization of the receptor by ligand blotting using 125iodine-vitellogenin after sodium dodecyl sulfate electrophoresis revealed the existence of one major binding component corresponding to a protein of 113 kDa. The Scatchard transformation of the binding data revealed a single class of binding sites with an apparent Kd of 1.8 x 10(-8) M/L. The variations of the binding characteristics (Kd and maximum binding) were investigated during vitellogenesis. This study revealed that the Kd was not affected by oocyte growth during vitellogenesis, but was highly decreased in ovulated eggs. The receptor number increased during the same period from 35 to 860 fM per oocyte, while the receptor number per mm2 of oocyte membrane surface was doubled during the same period.

Animals↗
PubMed1996

Vitellogenin receptors: oocyte-specific members of the low-density lipoprotein receptor supergene family.

Receptors that transport vitellogenin (VTG) into oocytes are of vital importance to egg-laying species, because they mediate a key step of oocyte maturation, a prerequisite to reproduction. Vitellogenins are lipophosphoglycoproteins that are produced under female hormonal control in large central organs (fat body in insects; liver in higher animals) and are transported in the circulation to the female gonads. VTG receptors localized in coated pits on the surface of growth-competent oocytes are able to accumulate in the yolk high concentrations of VTG and other ligands they recognize. The study of VTG receptors and their ligands has identified genes that specify related ligands, and a family of receptors. To date, all molecularly characterized VTG receptors belong to the low-density lipoprotein receptor supergene family, which ranges from a 600-kDa receptor in Caenorhabditis elegans to the 100-kDa so-called very-low-density lipoprotein receptors in mammals. These receptors, by and large, recognize ligands with similarities in structural elements first defined in the human apoplipoproteins B-100 and E. Recent studies on the receptor family have added VTG and lipoprotein lipase to the list of co-evolved ligands and have revealed that VTG receptors are able to interact with ligands other than VTG and also with some unrelated to lipoprotein metabolism. For example, the chicken VTG receptor also imports very-low-density lipoprotein, riboflavin-binding protein, and alpha-2-macroglobulin into growing oocytes. Such multifunctionality of receptors is likely the result of evolutionary pressure to provide the female germ cell with a highly economical machinery for vitellogenesis.

Animals↗
PubMed2006

Regulatory region of the vitellogenin receptor gene sufficient for high-level, germ line cell-specific ovarian expression in transgenic Aedes aegypti mosquitoes.

Vitellogenin receptor (VgR) is responsible for the receptor-mediated endocytosis of vitellogenin (Vg) in the egg formation of an oviparous animal, including insects. Little is known about regulation of VgR gene expression. We analyzed the upstream region of the VgR gene from Aedes aegypti (AaVgR) to identify regulatory elements responsible for its expression in germ cell-specific ovarian expression. Experiments with genetic transformation using the transgene containing the 1.5-Kb upstream portion of the AaVgR gene fused with DsRed and the piggyBac vector showed that this regulatory region is sufficient for correct female and ovary-specific expression of the transgene. This 1.5-Kb upstream region contained binding sites for the ecdysone regulatory hierarchy early gene products E74 and BR-C, as well as transcription factors determining correct tissue- and stage-specific expression of GATA and HNF3/fkh. In situ hybridization demonstrated that in the ovaries of transgenic females DsRed mRNA was present in ovarian germ cells and nurse cells of mature ovarian follicles, together with VgR mRNA. In contrast, DsRed mRNA was absent in the oocyte that had a high level of endogenous VgR mRNA. Although the 1.5-Kb upstream region was sufficient to drive a high-level germ line cell-specific expression of the reporter, additional signals were required for translocation of exogenous mRNA from nurse cells into the oocyte.

Aedes↗
PubMed2002

Vitellogenin-derived yolk proteins of white perch, Morone americana: purification, characterization, and vitellogenin-receptor binding.

The objectives of this study were to 1) purify and characterize vitellogenin-derived yolk proteins of white perch (Morone americana), 2) develop a nonisotopic receptor binding assay for vitellogenin, and 3) identify the yolk protein domains of vitellogenin recognized by the ovarian vitellogenin receptor. Four yolk proteins derived from vitellogenin (YP1, YP2 monomer [YP2m] and dimer [YP2d], and YP3) were isolated from ovaries of vitellogenic perch by selective precipitation, ion exchange chromatography, and gel filtration. The apparent molecular masses of purified YP1, YP2m, and YP2d after gel filtration were 310 kDa, 17 kDa, and 27 kDa, respectively. YP3 appeared in SDS-PAGE as a approximately 20-kDa band plus some diffuse smaller bands that could be visualized by staining for phosphoprotein with Coomassie Brilliant Blue complexed with aluminum nitrate. Immunological and biochemical characteristics of YP1, YP2s, and YP3 identified them as white perch lipovitellin, beta'-components, and phosvitin, respectively. A novel receptor-binding assay for vitellogenin was developed based on digoxigenin (DIG)-labeled vitellogenin tracer binding to ovarian membrane proteins immobilized in 96-well plates. Lipovitellin from white perch and vitellogenin from perch and other teleosts effectively displaced specifically bound DIG-vitellogenin in the assay, but phosvitin and the beta'-component could not, demonstrating for the first time that the lipovitellin domain of teleost vitellogenin mediates its binding to the oocyte receptor. Lipovitellin was less effective than vitellogenin in this regard, suggesting that the remaining yolk protein domains of vitellogenin may interact with its lipovitellin domain to facilitate binding of vitellogenin to its receptor.

Amino Acid Sequence↗
PubMed2004

cDNA cloning and transcriptional regulation of the vitellogenin receptor from the imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae).

We describe the cloning of the first hymenopteran vitellogenin receptor (VgR) cDNA from the imported fire ant, Solenopsis invicta, an invasive pest. Using reverse transcription polymerase chain reaction and rapid amplification of cDNA ends, fragments encompassing the entire coding region of a putative VgR were cloned and sequenced. The complete 5764 bp cDNA encodes a 1782 residue protein with a predicted molecular mass of 201.3 kDa (=SiVgR). Northern blot analysis demonstrated that the 7.4 kb SiVgR transcript was present only in ovaries of reproductive females (virgin alates and queens). The temporal profile of transcriptional expression showed that SiVgR mRNA increased with age in virgin alate females and that this was up-regulated by methoprene, a juvenile hormone (JH) analogue. This suggests that the SiVgR gene is JH regulated.

Age Factors↗
PubMed2006

Systemic RNAi of the cockroach vitellogenin receptor results in a phenotype similar to that of the Drosophila yolkless mutant.

During vitellogenesis, one of the most tightly regulated processes in oviparous reproduction, vitellogenins are incorporated into the oocyte through vitellogenin receptor (VgR)-mediated endocytosis. In this paper, we report the cloning of the VgR cDNA from Blattella germanica, as well as the first functional analysis of VgR following an RNA interference (RNAi) approach. We characterized the VgR, VgR mRNA and protein expression patterns in pre-adult and adult stages of this cockroach, as well as VgR immunolocalization in ovarioles, belonging to the panoistic type. We then specifically disrupted VgR gene function using RNAi techniques. Knockdown of VgR expression led to a phenotype characterized by low yolk content in the ovary and high vitellogenin concentration in the haemolymph. This phenotype is equivalent to that of the yolkless mutant of Drosophila melanogaster, which have the yl (VgR) gene disrupted. The results additionally open the perspective that development genes can be functionally analyzed via systemic RNAi in this basal species.

Animals↗
PubMed2004

Molecular characterization and expression of vitellogenin receptor from white perch (Morone americana).

A full-length (4021 base pair [bp]) cDNA encoding a polypeptide (844 amino acids) with a predicted mass of 93 kDa and other characteristic structural features of a vertebrate vitellogenin receptor (VgR) was isolated from a white perch (Morone americana) ovarian cDNA library. Northern blotting performed using a specific digoxygenin-labeled VgR cDNA probe revealed a distinct approximately 4.1 kilobase (kb) hybridization signal in an mRNA preparation obtained from previtellogenic perch ovaries. The deduced amino acid sequence of the perch VgR was 89% and 82% identical, respectively, to that of the tilapia and rainbow trout. Because it possessed an eight-repeat ligand-binding domain (LR8) but lacked an O-linked sugar domain (-), the perch VgR was identified as a non-O-linked form of VgR (LR8-). Unlike the case in other vertebrates investigated, including tilapia and trout, no species of mRNA encoding an O-linked form of VgR (LR8+) could be detected when perch ovarian or liver mRNA reverse transcripts or cDNA libraries were screened by PCR using primer sets flanking the putative O-linked sugar domain. These novel findings call into question the assumptions that an LR8+ splice variant of the VgR always is dominantly present in somatic tissues and exists at lower levels in ovarian tissues to sequester lipoproteins distinct from Vg. A SYBR-green-based real-time reverse transcription-polymerase chain reaction assay was developed and used to quantitatively measure VgR expression in gonadal and somatic tissues, for the first time in any vertebrate. The main site of perch VgR mRNA expression was the ovary and the highest level of VgR mRNA expression was in ovaries whose largest follicles contained previtellogenic oocytes. Expression of VgR mRNA decreased with oocyte growth during vitellogenesis and was very limited in ovulated eggs. These quantitative results verify the concept that growing oocytes must extensively recycle LR8- forms of the VgR.

Alternative Splicing↗
PubMed1996

Characterization of a vitellogenin receptor in white perch (Morone americana).

Receptors for white perch vitellogenin (wVTG) were characterized using wVTG, labeled in vivo with [3H]leucine or in vitro with 125I, and semipurified ovarian membranes. Specific binding of wVTG to the membranes was temperature-dependent, proportional to the amount of membrane, and saturable. Scatchard analyses revealed a single class of binding sites of low maximum binding capacity (MBC; approximately 35 pmol VTG/mg membrane protein) and high affinity (Kd approximately 400 nM), consistent with wVTG levels (540-2700 nM) circulating in maturing females. Ligand blotting revealed a receptor protein of M(r) approximately 157000 and a smaller protein, possibly its degradation product. Striped bass vitellogenin, chicken egg yolk very low density lipoprotein, and suramin displaced wVTG from its receptor, but BSA did not. No change in Kd was noted over the course of vitellogenesis in maturing perch, and MBC increased only slightly very late in the gametogenic cycle. The wVTG bound specifically to membranes prepared from liver, muscle, and mesenteric fat, but not to erythrocyte membranes. The Kd for ovary (394 nM) and liver (345 nM) were similar, but the Kd for muscle (1440 nM) was much higher.

Animals↗
PubMed1997

Identification of vitellogenin receptors in the ovary of a teleost fish, the Mediterranean sea bass (Dicentrarchus labrax).

The characterization of vitellogenin (VTG) receptors in ovarian membranes from vitellogenic female sea bass (Dicentrarchus labrax) is described. Incubation of membrane proteins with radiolabeled VTG (125I-VTG) after SDS-electrophoresis showed specific binding of 125I-VTG to a protein band of 100 kDa. Filter binding assays showed that binding of 125I-VTG to membrane receptors was saturable with increasing amounts of 125I-VTG. Scatchard analysis of the saturation data revealed a single class of binding sites with an apparent KD of 1.04 x 10(-8) M. The specificity of the VTG receptors was tested in competition assays; binding of 125I-VTG to ovarian membranes was completely abolished with an excess of purified sea bass VTG (cold VTG, VTG degree) or plasma from estradiol (E2)-treated fish, while the addition of control male plasma (without VTG) caused negligible effect.

Animals↗