Synthesis and characterization of a 29-amino acid residue DNA-binding peptide derived from α/β-type small, acid-soluble spore proteins (SASP) of bacteria

A 29-amino acid residue peptide (SASP-peptide) derived from the sequence of the putative DNA-contacting portion at the carboxyl terminus of an α/β-type small, acid-soluble spore protein (SASP) of Bacillus subillis has been synthesized by automated solid-phase methods and tested for its ability to interact with DNA. Circular dichroism (CD) spectroscopy reveals an interaction between this SASP-peptidc and DNA, both by an increase in α-helix content of the peplide (which alone has a mostly random conformation) and by enhancement of the 275-nm CD band of the DNA. In contrast to results with intact α/β-type SASP, however, the peptide does not induce a B → A cenformational transition in the DNA. The SASP-peptide also binds to poly(dG)·poly(dC) and prtects this polynucleotide against DNase I digestion and UV light-induced cylosine dimer formation, parallel to Findings made previously with native α/β-type SASP. The results confirm the hypothesis that the carboxyl-terminal region of the α/β-type SASP directly contacts DNA and possesses some, but not all, or the functional characteristics of the intact molecule.