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Abstract
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), while 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. Interestingly, PEST sites are
found in Vg sequences from other benthophil fish, while
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.
Key words:
Gamete Biology •
Developmental biology •
Gametogenesis •
Oocyte development
This article has been cited by other articles:
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  R. N. Finn The Maturational Disassembly and Differential Proteolysis of Paralogous Vitellogenins in a Marine Pelagophil Teleost: A Conserved Mechanism of Oocyte Hydration Biol Reprod, June 1, 2007; 76(6): 936 - 948. [Abstract] [Full Text] [PDF]
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R. N. Finn Vertebrate Yolk Complexes and the Functional Implications of Phosvitins and Other Subdomains in Vitellogenins Biol Reprod, June 1, 2007; 76(6): 926 - 935. [Abstract] [Full Text] [PDF]
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 D. Raldua, M. Fabra, M. G. Bozzo, E. Weber, and J. Cerda Cathepsin B-mediated yolk protein degradation during killifish oocyte maturation is blocked by an H+-ATPase inhibitor: effects on the hydration mechanism Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2006; 290(2): R456 - R466. [Abstract] [Full Text] [PDF]
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