Derivation of Major Yolk Proteins from Parental Vitellogenins and Alternative Processing During Oocyte Maturation in Fundulus heteroclitus

• Published in: Biology of reproduction Vol. 73; no. 4; pp. 815 - 824
• Main Authors: LAFLEUR, Gary J, RALDUA, Demetrio, FABRA, Mercedes, CARNEVALI, Oliana, DENSLOW, Nancy, WALLACE, Robin A, CERDA, Joan
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01-10-2005
• Subjects: Amino Acid Sequence; Animals; Biological and medical sciences; Cathepsin B - metabolism; Cathepsin L; Cathepsins - metabolism; Cells, Cultured; Conserved Sequence; Cysteine Endopeptidases - metabolism; Egg Proteins - metabolism; Female; Fundamental and applied biological sciences. Psychology; Fundulidae; Fundulus heteroclitus; Mammalian female genital system; Molecular Sequence Data; Morphology. Physiology; Oocytes - physiology; Sequence Analysis, Protein; Time Factors; Vertebrates: reproduction; Vitellogenins - metabolism; Steroid; gamete biology; Germinal cell; Vitellogenin; Cathepsin; Reproduction; maturation-inducing steroid; Proteolysis; Pisces; Development; Oocyte maturation; Hydration; Enzyme; Gametogenesis; developmental biology; oocyte development; Protein; free amino acids; Fundulus heteroclitus; Peptidases; Gamete; Vertebrata; Aminoacid; Hydrolases; killifish; Oocyte
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod.105.041335

Various Coomassie blue-staining yolk proteins (YPs) present in oocytes and eggs of Fundulus heteroclitus , a teleost that produces low hydrated, demersal eggs (benthophil species), were subjected to N-terminal microsequencing.
Four YPs were N-terminally blocked, while five yielded sequence information. Of the latter, four corresponded to internal
sequences of vitellogenin 1 (Vg1), whereas a fifth band corresponded to the N-terminal sequence of Vg2. Phosphorylated YPs
(phosvitins and phosvettes) derived from the polyserine domain of Vg were not successfully sequenced. The major N-terminally
blocked 122-and 103-kDa YPs both represented the lipovitellin heavy chain of Vg1 (LvH1), and thus most of the oocyte YPs were
derived from Vg1. During oocyte maturation in vivo and in vitro, the LvH1 122 is degraded, concomitant with an increased enzymatic
activity of cathepsin B, while the 45-kDa YP is converted to a 42-kDa YP. The LvH1 122 was found to contain a consensus site
for proteolytic degradation (PEST) near its C-terminus, which is missing from its stable, but truncated twin sequence, LvH1
103. We suggest that this site becomes exposed to cathepsin B during the hydration process that accompanies oocyte maturation
and renders the LvH1 122 susceptible to proteolysis. PEST sites are found in Vg sequences from other benthophil fish, whereas,
interestingly, they are missing in marine teleosts that spawn highly hydrated, pelagic eggs (pelagophil species), displaying
a different pattern of Vg incorporation into YPs and LvH1 and LvH2 processing to that found in F. heteroclitus . Thus, different models of Vg/YP precursor/product relationship and further processing during oocyte maturation and hydration
are proposed for pelagophil and benthophil teleosts.
Abstract
The vitellogenin/yolk protein precursor/product relationship and further processing during oocyte maturation in the teleost
Fundulus heteroclitus suggest different models of this mechanism for pelagophil and benthophil fish