B. Boldyreff et al., EXPRESSION AND CHARACTERIZATION OF A RECOMBINANT MAIZE CK-2 ALPHA-SUBUNIT, Biochimica et biophysica acta, 1173(1), 1993, pp. 32-38
CKIIB, one of the CK-2 like enzymes which have been isolated from maiz
e, has been shown to be a monomeric enzyme that cross-reacts with anti
CK-2 alpha specific antibodies suggesting a possible relationship bet
ween the two proteins (Dobrowolska et al. (1992) Eur. J. Biochem. 204,
299-303). In order to support the immunological data also by biochemi
cal and biophysical experiments the availability of a recombinant CK-2
alpha from maize was a prerequisite. A maize cDNA clone of maize CK-2
alpha was expressed in the bacterial strain BL21 (DE3). The recombina
nt protein was purified to homogeneity; its molecular mass on one-dime
nsional SDS PAGE was estimated to be 36.5 kDa. The calculated molecula
r mass according to the amino acid composition is 39 228 Da (332 amino
acids). The recombinant maize CK-2 alpha (rmCK-2 alpha) exhibited mos
tly the same properties as the recombinant human CK-2 alpha (rhCK-2 al
pha). In several respects it behaved differently from CKTIB, thus supp
orting the notion that either CKIIB is encoded by another gene or it u
ndergoes extensive posttranscriptional and/or posttranslational altera
tions. Three observations in particular disprove any close relatedness
between CKIIB and rmCK-2 alpha, namely: (a) the phosphorylation of ca
lmodulin by CKIIB is dramatically stimulated by polylysine, whereas po
lylysine inhibits rather than stimulating the phosphorylation of calmo
dulin by rmCK-2 alpha (and by rhCK-2 alpha). (b) Addition of rhCK-2 be
ta has no significant influence on the stimulation of the calmodulin p
hosphorylation by CKIIB whereas in the case of rmCK-2 alpha and rhCK-2
alpha addition of rhCK-2 beta is required for optimal stimulation by
polylysine. (c) CKIIB does not self-assemble with rhCK-2 beta to form
a high molecular mass complex as it is demonstrated for rmCK-2 alpha.