Structural studies on the signal sequence of E.coli ribose-binding protein by CD

Abstract

The structures of chemically synthesized funtional and nonfunctional signal peptides of Escherichia coli ribose binding protein were determined by CD in trifluoroethanol solution which mimmics the amphiphilic environment. The estimated value of helix content of the wild type was found to be 98\% at 25$^\circ$C and 86\% 50$^\circ$C. The estimated $\alpha$-helix content of the mutant peptide was 55\% at 25$^\circ$C and less than 10\% at 50$^\circ$C. It appeared that the Pro-9 residue in nonfunctional peptide disturbs the helix. Sine the $\alpha$-helix segment of the wild type signal peptide is longer than that of the mutant signal sequence, it appears that the necessary condition for the translocation of RBP is the dimension of the helix in the signal sequence.