High abundance calmodulin from Blattella germanica eggs binds to vitellin subunits but disappears during vitellin utilization
1992
Zhang, Y. | Kunkel, J.G.
A Ca2+-binding protein has been purified and characterized from Blattella germanica eggs. This protein has biochemical features in common with calmodulin (CaM). These common features include a relative low molecular weight of approximately 19 kDa, thermal stability, an acidic pI of 4.0, a low specific absorbance (E277nm 1% = 2.9), an altered electrophoretic mobility in SDS-polyacrylamide gels in the presence of 1 mM Ca2+, and calcium-dependent binding to the CaM antagonist W-7. These features, considered together with activation of CaM-dependent phosphodiesterase in a Ca2+-dependent manner and cross-reactivity with anti-bovine brain CaM antibody, are sufficient to define this protein as bone fide CaM. CaM comprises 1-1.5% of soluble protein of newly ovulated eggs depending on the mode of assay. A rabbit antibody specific for the B. germanica CaM cross-reacts with bovine brain CaM. 14C-labeled cockroach CaM in a gel-overlay technique binds to vitellin, the major yolk protein of B. germanica egg. The CaM-binding site of vitellin is located on the 95 kDa subunit before degradation and 53 kDa fragment after 95 kDa subunit breakdown. There is sufficient CaM to bind stoichiometrically (1:1) with the vitellin trimer. CaM is present at uniformly high levels until vitellin utilization starts then it is undetectable until the pharate larval stage at the end of embryogenesis.
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