The conformation of interfacially adsorbed Ranaspumin-2 Is an arrested state on the unfolding pathway

Morris, R. J., Brandani, G. B., Desai, V., Smith, B. O. , Schor, M. and MacPhee, C. E. (2016) The conformation of interfacially adsorbed Ranaspumin-2 Is an arrested state on the unfolding pathway. Biophysical Journal, 111(4), pp. 732-742. (doi:10.1016/j.bpj.2016.06.006) (PMID:27558717)

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Abstract

Ranaspumin-2 (Rsn-2) is a surfactant protein found in the foam nests of the túngara frog. Previous experimental work has led to a proposed model of adsorption that involves an unusual clam-shell-like unhinging of the protein at an interface. Interestingly, there is no concomitant denaturation of the secondary structural elements of Rsn-2 with the large-scale transformation of its tertiary structure. In this work we use both experiment and simulation to better understand the driving forces underpinning this unusual process. We develop a modified Gō-model approach where we have included explicit representation of the side chains to realistically model the interaction between the secondary structure elements of the protein and the interface. Doing so allows for the study of the underlying energy landscape that governs the mechanism of Rsn-2 interfacial adsorption. Experimentally, we study targeted mutants of Rsn-2, using the Langmuir trough, pendant drop tensiometry, and circular dichroism, to demonstrate that the clam-shell model is correct. We find that Rsn-2 adsorption is in fact a two-step process: the hydrophobic N-terminal tail recruits the protein to the interface after which Rsn-2 undergoes an unfolding transition that maintains its secondary structure. Intriguingly, our simulations show that the conformation Rsn-2 adopts at an interface is an arrested state along the denaturation pathway. More generally, our computational model should prove a useful, and computationally efficient, tool in studying the dynamics and energetics of protein-interface interactions.

Item Type:Articles
Additional Information:This work was funded by Engineering and Physical Sciences Research Council grant No. EP/J007404.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Smith, Dr Brian
Authors: Morris, R. J., Brandani, G. B., Desai, V., Smith, B. O., Schor, M., and MacPhee, C. E.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Biophysical Journal
Publisher:Biophysical Society
ISSN:0006-3495
ISSN (Online):1542-0086

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