Two forms of vitellogenin, yielding two distinct lipovitellins, play different roles during oocyte maturation and early development of barfin flounder, Verasper moseri, a marine teleost that spawns pelagic eggs
T. Matsubara et al., Two forms of vitellogenin, yielding two distinct lipovitellins, play different roles during oocyte maturation and early development of barfin flounder, Verasper moseri, a marine teleost that spawns pelagic eggs, DEVELOP BIO, 213(1), 1999, pp. 18-32
Two forms of vitellogenin (Vg), Vg A and Vg B, were identified in serum fro
m estrogen-treated barfin flounder (Verasper moseri). Structural changes of
lipovitellins (Lvs) derived from the two Vgs were examined during vitellog
enesis and oocyte maturation. Two Lvs, vLv A and vLv B, were identified ele
ctrophoretically and immunologically in postvitellogenic oocytes. Each appe
ared to be composed of distinct heavy chains (vLvH A, M-r 107,000, and vLvH
B, M-r 94,000) and light chains (vLvL A, M-r 30,000, and vLvL B, M-r 28,00
0) when analyzed by SDS-PAGE. Results from N-terminal amino acid sequencing
and Western blotting using antisera to vLvH A and vLvH B verified that the
re are two Vg polypeptides in serum from estrogen-treated fish, Vg A (M-r 1
68,000) and Vg B (M-r 175,000), which give rise to vLvH A-vLvL A and vLvH B
-vLvL B, respectively. N-terminal sequencing revealed two sequences for bot
h phosvitin and beta-component, supporting the concept of duality for all t
hree classes of Vg-derived yolk proteins. During oocyte maturation, native
dimeric vLv B was dissociated into a native M, 170,000 monomer (oLv B). Mea
nwhile, vLv A was extensively cleaved including complete degradation of vLv
H A into free amino acids. We propose that the quantitative ratio of vLv A
to vLv B in postvitellogenic. oocytes regulates the buoyancy of the spawned
pelagic eggs by controlling availability of free amino acids which functio
n as osmotic effecters during oocyte hydration. The vLv A/vLv B ratio likel
y also controls the proportional availability of different types of nutrien
ts, free amino acids versus Lv, for use during embryonic development. (C) 1
999 Academic Press.