title: Transfer of noncovalent chiral information along an optically inactive helical peptide chain: allosteric control of asymmetry of the C-terminal site by external molecule that binds to the N-terminal site.
abstract: This study aims at demonstrating end-to-end transfer of noncovalent chiral information along a peptide chain. The domino-type induction of helical sense is proven by using achiral peptides 1-m of bis-chromophoric sequence with different chain lengths: H-(Aib-Delta(Z)Phe)(m)-(Aib-Delta(Z)Bip)(2)-Aib-OCH(3) [m = 2, 4, and 6; Aib = alpha-aminoisobutyric acid; Delta(Z)Phe = (Z)-alpha,beta-didehydrophenylalanine; Delta(Z)Bip = (Z)-beta-(4,4'-biphenyl)-alpha,beta-didehydroalanine]. They all showed the tendency to adopt a 3(10)-helix. Whereas peptide 1-m originally shows no circular dichroism (CD) signals, marked CD signals were induced at around 270-320 nm based on both the beta-aryl didehydroresidues by chiral Boc-proline (Boc = tert-butoxycarbonyl). The observed CD spectra were interpreted on the basis of the exciton chirality method and theoretical CD simulation of several helical conformations that were energy-minimized. The experimental and theoretical CD analysis reveals that Boc-l-proline induces the preference for a right-handed helicity in the whole chain of 1-m. Such noncovalent chiral induction was not observed in the corresponding N-terminally protected 1-m. Obviously, helicity induction in 1-m originates from the binding of Boc-proline to the N-terminal site. In the 17-mer (1-6), the information of helix sense reaches the 16th residue from the N-terminus. We have monitored precise transfer of noncovalent chiral stimulus along a helical peptide chain. The present study also proposes a primitive allosteric model of a single protein-mimicking backbone. Here chiral molecule binding the N-terminal site of 1-6 controls the chiroptical signals and helical sense of the C-terminal site about 30 A away.
authors.affiliation: Department of Environmental Technology and Urban Planning, Shikumi College, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ousaka
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Inai
mesh_terms: D000042:Absorption; D000494:Allosteric Regulation; D032701:Biomimetics; D002942:Circular Dichroism; D003198:Computer Simulation; D008958:Models, Molecular; D055620:Optical Phenomena; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D010455:Peptides; D011506:Proteins