Human p8 is a HMG-I/Y-like protein with DNA binding activity enhanced by phosphorylation

We have studied the biochemical features, the conformational preferences in solution, and the DNA binding properties of human p8 (hp8), a nucleoprotei n whose expression is affected during acute pancreatitis. Biochemical studi es show that hp8 has properties of the high mobility group proteins, HMG-I/ Y, Structural studies have been carried out by using circular dichroism (ne ar- and far-ultraviolet), Fourier transform infrared, and NMR spectroscopie s. All the biophysical probes indicate that hp8 is monomeric (up to 1 mM co ncentration) and partially unfolded in solution. The protein seems to bind DNA weakly, as shown by electrophoretic gel shift studies. On the other han d, hp8 is a substrate for protein kinase A (PKA), The phosphorylated hp8 (P KAhp8) has a higher content of secondary structure than the nonphosphorylat ed protein, as concluded by Fourier transform infrared studies. PKAhp8 bind s DNA strongly, as shown by the changes in circular dichroism spectra, and gel shift analysis. Thus, although there is not a high sequence homology wi th HMG-I/Y proteins, hp8 can be considered as a HMG-I/Y-like protein.