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Acidification of yolk granules in Blattella germanica eggs coincident with proteolytic processing of vitellin
Author(s) -
Nordin John H.,
Beaudoin Esther L.,
Liu Xiaodong
Publication year - 1991
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940180306
Subject(s) - yolk , biology , cockroach , oocyte , incubation , oocyte activation , granule (geology) , biochemistry , medicine , endocrinology , food science , embryo , microbiology and biotechnology , ecology , paleontology
In eggs of the cockroach Blattella germanica , vitellin (Vt) utilization by the embryo is initiated at day 4 postovulation by the proteolytic processing of its three subunits to a specific set of peptides. A report from our laboratory (Nordin et al.: Archives of Insect Biochemistry and Physiology 15 :119, 1990) described a yolk proteinase, activated at days 3–4, which processes the Vt. Further investigation of this event has focused on the yolk granules. Granules from eggs 4–6 days postovulation contained a significant subpopulation which accumulated high concentrations of the dye acridine orange (AO), a fluorescent probe of vesicle acidification, while those from eggs 0–3 days postovulation did not. AO accumulation was caused by proton translocation and was not due to dye binding or a Donnan equilibrium. The temporal correlation of granule acidification with Vt processing suggests a role for this event in yolk proteinase activation in B. germanica . This hypothesis was supported by the finding that incubation of yolk from freshly ovulated eggs in vitro at pH of 5 and below resulted in Vt processsing. Yolk granules of the blowfly Phormia regina also became acidified but this occurred in the oocyte prior to egg deposition.