Investigation of folding in protamine by FTIR.
The secondary structure of purified protamine, a non-specific DNA binding protein, was studied in solution at pH 4, 7 and 8 by FTIR. This permitted analysis of the folded form of the protein (acidic pH) as well as the folded conformers (neutral and basic pH). Hg(2+) was utilized to probe the accessibility of the free thiol groups (cysteine residues). The SH groups form when disulfides, which play the major role in stabilizing the conformation of this protein, are broken. It was possible to observe different conformational states in protamine as a function of pH and the presence of Hg(2+) via spectral changes primarily in the amide region. The results lead to the conclusion that protamine is not completely folded under conditions similar to those found in vivo (37 degrees , neutral pH, phosphate buffer and high protein concentration).
Pesek
J J
JJ
Department of Chemistry, San Jose State University, San Jose, CA 95192, U.S.A.
Shabary
F R
FR