Binding studies of a triple-helical peptide model of macrophage scavenger receptor to tetraplex nucleic acids.
The macrophage scavenger receptor (MSR), involved in the uptake of oxidized LDL, binds a variety of polyanionic ligands, and in particular shows selectivity for tetraplex forms of nucleic acids. The ligand binding region has been shown to lie in the triple-helical collagen-like domain of MSR. A model peptide-nucleic acid system is presented here to clarify how the triple-helical motif of MSR recognizes and binds tetraplex nucleic acids. The triple-helical peptide MSR-1, with the sequence (POG)3PKGQKGEKG(POG)4, contains a nine amino acid basic sequence implicated in MSR ligand binding, flanked by Pro-Hyp-Gly triplets to provide stability. The ability of this triple-helical MSR-1 peptide to bind to and perturb the conformation of nucleic acids in tetraplex, duplex, and single-stranded states was assessed by monitoring changes in the nucleic acid circular dichroism spectrum in the 240-300 nm region. Our results show that the triple-helical MSR-1 peptide binds to tetraplex poly(I) in a stoichiometric manner and is capable of reproducing the discrimination exhibited by the native MSR molecule for tetraplex over double-stranded or single-stranded nucleic acid states. The triple-helical reference peptide (POG)10 does not bind to tetraplex poly(I), suggesting that binding requires the highly basic 9-mer sequence from MSR that is included in MSR-1. The MSR-1 peptide did not perturb the CD spectra of a series of other tetraplex nucleic acids, indicating that it does not model the broader specificity that MSR shows under physiological conditions. Models of possible interactions between a triple-helical peptide and a tetraplex polynucleotide are proposed on the basis of the stoichiometry observed for the complex between triple-helical MSR-1 and tetraplex poly(I).
Mielewczyk
S S
SS
Department of Chemistry, Rutgers, State University of New Jersey, Piscataway 08855, USA.
Breslauer
K J
KJ
Anachi
R B
RB
Brodsky
B
B
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D011069:Poly I / Q000737:chemistry / Q000378:metabolism; D011119:Polynucleotides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011971:Receptors, Immunologic / Q000737:chemistry / Q000378:metabolism*; D051116:Receptors, Scavenger
D010455:Peptides; D011119:Polynucleotides; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; D011069:Poly I