Conformational ensembles of neuromedin C reveal a progressive coil-helix transition within a binding-induced folding mechanism

Abstract

Abstract:Neuromedin C (NMC) is a peptide that regulates various processes in the central nervous system and gastrointestinal tract through its interaction with the bombesin receptor subtype-2 (BB2R). Hence, BB2R antagonists hold potential to treat disorders that occur as a result of NMC dysfunction or misregulation. However, their efficient design requires a detailed understanding of the structural features of NMC, which hitherto are unknown. Here we describe the conformational ensembles of NMC in aqueous solution, at five different TFE concentrations to decode its folding pathway, and under its SDS micelle bound state that likely resembles the receptor-triggered conformation. NMC displays a disordered but well-defined backbone architecture that undergoes a progressive coil-helix transition with increasing TFE concentrations, first at the C-terminus and then at the N-terminus. NMC also adopts a C-terminal α-helical conformation upon binding to SDS micelles. This micelle binding is directed by hydrophobic interactions that concur with the unfavorable deprotonation of His8 and its further insertion into the micelle. Moreover, NMR relaxation data reveal that the acquisition of the micelle bound α-helical conformation constrains the NMC flexibility more than the confinement itself. This comprehensive study of the structural behavior of NMC provides essential mechanistic information for the development of new Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporationtherapeutics to treat neurological, cancer-related or eating disorders.Author Comments: Dear Editor,We would like to submit our manuscript entitled "Conformational ensembles of neuromedin C reveal a progressive coil-helix transition within a binding-induced folding mechanism" to be considered for publication in Chemistry A-European Journal.Neuromedin C (NMC) is a decapeptide that regulates different biological process in the central nervous system and in the gastrointestinal tract. For instance, NMC modulates appetite, participates in neurotransmission, and regulates growth and differentiation of tumors. All these processes are mediated through its interaction with the subtype-2 bombesin receptor (BB2R), which is a member of the G-protein coupled receptor superfamily. Thus, BB2R antagonists are considered as potential therapeutics and their efficient design will benefit from the understanding of the structural features of NMC.At present, the available structural information on NMC is very limited. Therefore, we provide a comprehensive description of the structural behavior of NMC in the accompanying manuscript. Different biophysical techniques (nuclear magnetic resonance, fluorescence, circular dichroism and isothermal titration calorimetry) were used to characterize the conformations of NMC in aqueous solution. We calculated the solution structure of NMC at increasing TFE concentrations in order to describe at residue level the pathway involved in its coil-helix transition, a process that likely mimics the receptor interaction. T...