An Alpha Helix Conformationally Restricted Peptide Is Recognized by Cervical Carcinoma Patients' Sera

Abstract

Human papillomavirus type 16 (HPV-16) represents the major cervical carcinoma associated virus among women, especially in Colombia. It has thus become important to develop reliable inexpensive tests for detecting the presence of this virus. It has been shown that HPV16-E7 oncoprotein structural features have three alpha-helical structures and a loop-like structure. The hydrazone link approach was used to mimic helix secondary substructures. Sera from women with invasive cervical carcinoma were tested against conformationally restricted peptides and their respective linear peptides to identify conformational epitopes. One peptide that was conformationally restricted to an alpha-helix showed very strong positive reaction with sera from women having invasive cervical carcinoma; there was no reaction with sera from patients with other carcinomas, children, or healthy women. NMR studies confirmed this peptide's alpha-helical structure. The observation that constrained protein substructure peptidomimetics can identify new conformationally sensitive antibodies in cervical carcinoma patients' sera is very important, since these antibodies are almost all generated by native proteins, providing a new selection of antibodies for diagnostic and vaccine studies.

Scaffolds for Blocking Protein-Protein Interactions

“…The modified peptide was found to bind to BCL-2 with a K d value of 38.8 nM via a fluorescence polarization assay, more than a sixfold increase over the unmodified BID BH3 peptide (K d = 269 nM). Additional strategies for constraining -helices, recently reported to probe protein-protein interactions, include macrolactam formation [69], disulfide bridge formation [70], and hydrogen-bond surrogate formation [71], as well as the use of , diaminoalkane crosslinking tethers [72]. These studies highlight the importance of constrained -helical secondary structure for the inhibition of a variety of protein-protein interactions.…”

Development of small molecules designed to modulate protein–protein interactions

“…Such artificial helical peptides are attractive scaffolds for molecular recognition, since the main chain H-bond surrogate either blocks solventexposed recognition surface or removes important side chain functionalities. For example, one peptide analog of a human papillomavirus peptide segment was conformationally restricted to an a-helix structure using the hydrazone link (N-H=CH-CH2CH2) approach and was shown to have a very strong reaction with sera from women having invasive cervical carcinoma [87].…”

Conformational HER-2/neu B-cell Epitope Peptide Vaccine Designed to Incorporate Two Native Disulfide Bonds Enhances Tumor Cell Binding and Antitumor Activities

“…The rational design of peptides that incorporate certain secondary and tertiary structural characteristics has had important implications in vaccine development (30,44,45). Recently, Calvo et al (46), investigated the use of conformational epitopes from the human papillomavirus type 16-E7 oncoprotein as a diagnostic tool for identifying the presence of HPV16 in cervical cancer patients. They synthesized a series of conformational peptides as well as their linear counterparts and demonstrated that sera isolated from patients with invasive cervical carcinoma showed strong reactivity to an ␣-helical peptide.…”