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Conformation and molecular topography of the N-terminal segment of surfactant protein B in structure-promoting environments

Gordon, Larry M. and Horvath, Suzanna and Longo, Marjorie L. and Zasadzinski, Joseph A. N. and Taeusch, H. William and Faull, Kym and Leung, Carol and Waring, Alan J. (1996) Conformation and molecular topography of the N-terminal segment of surfactant protein B in structure-promoting environments. Protein Science, 5 (8). pp. 1662-75. ISSN 0961-8368. PMCID PMC2143483. https://resolver.caltech.edu/CaltechAUTHORS:20170408-202428272

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Abstract

Although the effects of surfactant protein B (SP-B) on lipid surface activity in vitro and in vivo are well known, the relationship between molecular structure and function is still not fully understood. To further characterize protein structure-activity correlations, we have used physical techniques to study conformation, orientation, and molecular topography of N-terminal SP-B peptides in lipids and structure-promoting environments. Fourier transform infrared (FTIR) and CD measurements of SP-B_(1-25) (residues 1-25) in methanol, SDS micelles, egg yolk lecithin (EYL) liposomes, and surfactant lipids indicate the peptide has a dominant helical content, with minor turn and disordered components. Polarized FTIR studies of SP-B_(1-25) indicate the long molecular axis lies at an oblique angle to the surface of lipid films. Truncated peptides were similarly examined to assign more accurately the discrete conformations within the SP-B_(1-25) sequence. Residues Cys-8-Gly-25 are largely alpha-helix in methanol, whereas the N-terminal segment Phe-1-Cys-8 had turn and helical propensities. Addition of SP-B_(1-25) spin-labeled at the N-terminal Phe (i.e., SP-B^*_(1-25)) to SDS, EYL, or surfactant lipids yielded electron spin resonance spectra that reflect peptide bound to lipids, but retaining considerable mobility. The absence of characteristic radical broadening indicates that SP-B_(1-25) is minimally aggregated when it interacts with these lipids. Further, the high polarity of SP-B_(1-25) argues that the reporter on Phe-1 resides in the headgroup of the lipid dispersions. The blue-shift in the endogenous fluorescence of Trp-9 near the N-terminus of SP-B_(1-25) suggests that this residue also lies near the lipid headgroup. A summary model based on the above physical experiments is presented for SP-B_(1-25) interacting with lipids.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/pro.5560050820DOIArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2143483/PubMed CentralArticle
Additional Information:© 1996 The Protein Society. (RECEIVED December 5, 1995; ACCEPTED May 21, 1996) We thank Dr. Larry Vickery (UC Irvine) for use of the Jasco 5-720 CD spectrometer and Dr. James Bowie (UCLA) for use of the AVIV 62DS spectropolarimeter. We acknowledge Conrado Savilla I11 and John Racs for their help with the synthesis and cleavage of the spin-labeled SP-B peptides. Special thanks to Dr. Maria Mas for access to the Beckman City of Hope Molecular Modeling Facility, and to Dr. Mark Sherman for assistance in modeling the peptide-lipid ensemble in the BIOGRAF environment. We are grateful to Dr. Tim Wiedman for sharing prepublication, residue-specific 2D NMR data on a synthetic peptide comprising the N-terminal helical segment of SP-B. We also thank the reviewers, Mike Lipp, and Ka Yee Lee for their helpful comments on the manuscript. This study was supported by NIH grant HL 40666 (H.W.T., A.W., L.G.), HL 55534 and RCMI G12 RR 3026 (A.W., L.G.),and HL 51177-02 (J.J.Z.). The AB1 431A peptide synthesizer was acquired by an NIH small equipment grant GM 50483 (A.W., L.G.).
Funders:
Funding AgencyGrant Number
NIHHL 40666
NIHHL 55534
NIHRCMI G12 RR 3026
NIHGM 50483
Subject Keywords:CD spectroscopy; ESR spectroscopy; fluorescence; FTIR spectroscopy; lipid-peptide interactions; N-terminal domain; surfactant protein B
Issue or Number:8
PubMed Central ID:PMC2143483
Record Number:CaltechAUTHORS:20170408-202428272
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170408-202428272
Official Citation:Gordon LM, Horvath S, Longo ML, et al. Conformation and molecular topography of the N-terminal segment of surfactant protein B in structure-promoting environments. Protein Science : A Publication of the Protein Society. 1996;5(8):1662-1675.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76384
Collection:CaltechAUTHORS
Deposited By: 1Science Import
Deposited On:30 Mar 2018 22:38
Last Modified:03 Oct 2019 17:00

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