Oriano Marin

Functional analysis of CK2β-derived synthetic fragments

Synthetic peptides reproducing the amino and carboxyl terminal region of CK2 β subunit have been analyzed for their ability to mimic different properties of full length β subunit. Peptide β[1–77], containing both the autophosphorylation site and the down-regulatory domain 55–l64, is readily phosphorylated by α subunit whose activity is concomitantly inhibited. Such inhibition is accompanied by a weak interaction detectable by BIAcore sensograms but not by far Western blots, and is not reversed by polylysine which conversely overcome inhibition of calmodulin phosphorylation by full length β subunit. A strong interaction with α is observed with β[155–215] but not with its shorter derivative β[170–215] as judged from far Western blotting and sucrose gradient ultracentrifugation analysis. Both peptides, however, affect the regular interaction between α and β subunits altering the autophosphorylation pattern and responsiveness to salt. β[ 155–215], unlike β[ 170–215] tends to aggregate more readily than full length β subunit. This behaviour which is reminiscent of the homodimerization of full length β subunit, would indicate that tight self-association of β[ 155–215] crucially depends on residues in the 155–170 sequence. Failure of β[1–77] fragment to mediate responsiveness to polybasic peptides and accentuated self-association propensity of β[ 155–215] suggest that other structural elements between the sequences 1–77 and 155–215 are required in order to confer optimal functionality to the β subunit. (Mol Cell Biochem 191: 35–42, 1999).