Studies of the structure of bacteriophage λ cro protein in solution : Analysis of the circular dichroism data

Abstract

The secondary and tertiary structures of bacteriophage cro protein were studied by circular dichroism. The pH dependence of this structure was investigated; cro protein is stable over pH 4.5–10.5. At these pH-values cro protein contains ≈35% α-helix, ≈20% antiparallel β-structure and ≈15% β-turn, while the remaining part of the protein molecule is in the irregular state. The secondary and tertiary structures of the protein are modified abruptly at more acid and more alkaline pH-values. The curves characterizing the secondary and tertiary structures of the protein are symbatic. The effect of Gu—HCl on the secondary and tertiary structures of cro protein at 22°C and pH 7.2 was studied also. The conformational transition occurs within 0.6–1.9 M Gu—HCl. The changes in the secondary and tertiary structures of the protein have a symbatic character. Thermal denaturation of cro protein was examined. A possible mechanism of the protein denaturation is discussed.