Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B

Assembly of pulmonary surfactant lipid-protein complexes depends on conformational changes coupled with proteolytic maturation of proSP-B, the precursor of pulmonary surfactant protein B (SP-B), along the surfactant biogenesis pathway in pneumocytes. Conformational destabilization of the N-terminal...

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Main Authors:	Bañares-Hidalgo, Ángeles, Pérez-Gil, Jesús, Estrada, Pilar
Format:	Online
Language:	English
Published:	Public Library of Science 2016
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4933373/

id	pubmed-4933373
recordtype	oai_dc
spelling	pubmed-49333732016-07-18 Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B Bañares-Hidalgo, Ángeles Pérez-Gil, Jesús Estrada, Pilar Research Article Assembly of pulmonary surfactant lipid-protein complexes depends on conformational changes coupled with proteolytic maturation of proSP-B, the precursor of pulmonary surfactant protein B (SP-B), along the surfactant biogenesis pathway in pneumocytes. Conformational destabilization of the N-terminal propeptide of proSP-B (SP-BN) triggers exposure of the mature SP-B domain for insertion into surfactant lipids. We have studied the conformational stability during GdmCl- or urea-promoted unfolding of SP-BN with trp fluorescence and circular dichroism spectroscopies. Binding of the intermediate states to bis-ANS suggests their molten globule-like character. ΔG0H2O was ~ 12.7 kJ·mol-1 either with urea or GdmCl. None of the thermal transitions of SP-BN detected by CD correspond to protein unfolding. Differential scanning calorimetry of SP-BN evidenced two endothermic peaks involved in oligomer dissociation as confirmed with 2 M urea. Ionic strength was relevant since at 150 mM NaCl, the process originating the endotherm at the highest temperature was irreversible (Tm2 = 108.5°C) with an activation energy of 703.8 kJ·mol-1. At 500 mM NaCl the process became reversible (Tm2 = 114.4°C) and data were fitted to the Non-two States model with two subpeaks. No free thiols in the propeptide could be titrated by DTNB with or without 5.7 M GdmCl, indicating disulfide bonds establishment. Public Library of Science 2016-07-05 /pmc/articles/PMC4933373/ /pubmed/27380171 http://dx.doi.org/10.1371/journal.pone.0158430 Text en © 2016 Bañares-Hidalgo et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Bañares-Hidalgo, Ángeles Pérez-Gil, Jesús Estrada, Pilar
spellingShingle	Bañares-Hidalgo, Ángeles Pérez-Gil, Jesús Estrada, Pilar Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B
author_facet	Bañares-Hidalgo, Ángeles Pérez-Gil, Jesús Estrada, Pilar
author_sort	Bañares-Hidalgo, Ángeles
title	Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B
title_short	Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B
title_full	Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B
title_fullStr	Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B
title_full_unstemmed	Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B
title_sort	conformational stability of the nh2-terminal propeptide of the precursor of pulmonary surfactant protein sp-b
description	Assembly of pulmonary surfactant lipid-protein complexes depends on conformational changes coupled with proteolytic maturation of proSP-B, the precursor of pulmonary surfactant protein B (SP-B), along the surfactant biogenesis pathway in pneumocytes. Conformational destabilization of the N-terminal propeptide of proSP-B (SP-BN) triggers exposure of the mature SP-B domain for insertion into surfactant lipids. We have studied the conformational stability during GdmCl- or urea-promoted unfolding of SP-BN with trp fluorescence and circular dichroism spectroscopies. Binding of the intermediate states to bis-ANS suggests their molten globule-like character. ΔG0H2O was ~ 12.7 kJ·mol-1 either with urea or GdmCl. None of the thermal transitions of SP-BN detected by CD correspond to protein unfolding. Differential scanning calorimetry of SP-BN evidenced two endothermic peaks involved in oligomer dissociation as confirmed with 2 M urea. Ionic strength was relevant since at 150 mM NaCl, the process originating the endotherm at the highest temperature was irreversible (Tm2 = 108.5°C) with an activation energy of 703.8 kJ·mol-1. At 500 mM NaCl the process became reversible (Tm2 = 114.4°C) and data were fitted to the Non-two States model with two subpeaks. No free thiols in the propeptide could be titrated by DTNB with or without 5.7 M GdmCl, indicating disulfide bonds establishment.
publisher	Public Library of Science
publishDate	2016
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4933373/
_version_	1613604433631903744

Conformational Stability of the NH2-Terminal Propeptide of the Precursor of Pulmonary Surfactant Protein SP-B

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