Meggio F, Boldyreff B, Marin O, Pinna L A, Issinger O G
Dipartimento di Chimica Biologica, Università di Padova, Italy.
Eur J Biochem. 1992 Feb 15;204(1):293-7. doi: 10.1111/j.1432-1033.1992.tb16636.x.
Recombinant human alpha subunit from casein kinase-2 (CK-2) was subjected, either alone or in combination with recombinant human beta subunit, to high temperature, tryptic digestion and urea treatment. In all three cases, it was shown that the presence of the beta subunit could drastically reduce the loss of kinase activity, strongly suggesting a protective function for the beta subunit. Assaying different peptides for specificity toward the recombinant alpha subunit and the recombinant reconstituted enzyme, showed that the presence of the beta subunit could modify the specificity of the catalytic alpha subunit. Therefore, a dual function for the beta subunit is proposed which confers both specificity and stability to the catalytic alpha subunit within the CK-2 holoenzyme complex. The peptide DLEPDEELEDNPNQSDL, reproducing the highly acidic amino acid 55-71 segment of the human beta subunit, counteracts the stimulatory effect of the beta subunit on the alpha subunit activity and partially substitutes the beta subunit in conferring thermal stability to the alpha subunit. No such effect is induced by the peptide MSSSEEVSW, reproducing the N-terminal segment of the beta subunit including the autophosphorylation site. It is suggested that the acidic domain of the beta subunit, encompassing residues 55-71, plays a role in the interactions between the beta and alpha subunits.
酪蛋白激酶2（CK-2）的重组人α亚基单独或与重组人β亚基联合，接受高温、胰蛋白酶消化和尿素处理。在所有这三种情况下，结果表明β亚基的存在可显著减少激酶活性的丧失，强烈提示β亚基具有保护功能。检测不同肽对重组α亚基和重组复性酶的特异性，结果表明β亚基的存在可改变催化性α亚基的特异性。因此，提出β亚基具有双重功能，可赋予CK-2全酶复合物中的催化性α亚基特异性和稳定性。肽DLEPDEELEDNPNQSDL可重现人β亚基高度酸性的氨基酸55-71片段，它可抵消β亚基对α亚基活性的刺激作用，并在赋予α亚基热稳定性方面部分替代β亚基。肽MSSSEEVSW可重现β亚基包括自磷酸化位点的N端片段，它不会诱导这种效应。提示β亚基包含55-71位残基的酸性结构域在β亚基与α亚基之间的相互作用中发挥作用。
