Environmental Pollutant Ozone Causes Damage to Lung Surfactant Protein B (SP-B).
Lung surfactant protein B (SP-B) is an essential protein found in the surfactant fluid at the air-water interface of the lung. Exposure to the air pollutant ozone could potentially damage SP-B and lead to respiratory distress. We have studied two peptides, one consisting of the N-terminus of SP-B [SP-B(1-25)] and the other a construct of the N- and C-termini of SP-B [SP-B(1-25,63-78)], called SMB. Exposure to dilute levels of ozone (~2 ppm) of monolayers of each peptide at the air-water interface leads to a rapid reaction, which is evident from an increase in the surface tension. Fluorescence experiments revealed that this increase in surface tension is accompanied by a loss of fluorescence from the tryptophan residue at the interface. Neutron and X-ray reflectivity experiments show that, in contrast to suggestions in the literature, the peptides are not solubilized upon oxidation but rather remain at the interface with little change in their hydration. Analysis of the product material reveals that no cleavage of the peptides occurs, but a more hydrophobic product is slowly formed together with an increased level of oligomerization. We attributed this to partial unfolding of the peptides. Experiments conducted in the presence of phospholipids reveal that the presence of the lipids does not prevent oxidation of the peptides. Our results strongly suggest that exposure to low levels of ozone gas will damage SP-B, leading to a change in its structure. The implication is that the oxidized protein will be impaired in its ability to interact at the air-water interface with negatively charged phosphoglycerol lipids, thus compromising what is thought to be its main biological function.
Department of Biological Sciences and Institute of Structural and Molecular Biology, Birkbeck College, University of London , Malet Street, London WC1E 7HX, U.K.
Joanna M
JM
Hemming
Department of Biological Sciences and Institute of Structural and Molecular Biology, Birkbeck College, University of London , Malet Street, London WC1E 7HX, U.K.
Brian R
BR
Hughes
Materials Physics, Department of Physics and Astronomy, Uppsala University , 75120 Uppsala, Sweden.
Adrian R
AR
Rennie
Department of Biological Sciences and Institute of Structural and Molecular Biology, Birkbeck College, University of London , Malet Street, London WC1E 7HX, U.K.
Salvador
S
Tomas
Institut Laue-Langevin , 71 Avenue des Martyrs, CS20156, 38042 Grenoble Cedex 09, France.
Richard A
RA
Campbell
ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory , Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K.
Arwel V
AV
Hughes
Diamond Light Source , Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
Thomas
T
Arnold
STFC, Lasers for Science Facility, Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory , Harwell Oxford, Didcot, Oxfordshire OX11 0FA, U.K.
Stanley W
SW
Botchway
Department of Biological Sciences and Institute of Structural and Molecular Biology, Birkbeck College, University of London , Malet Street, London WC1E 7HX, U.K.
Katherine C
KC
Thompson
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D000388:Air / Q000032:analysis; D000595:Amino Acid Sequence; D004785:Environmental Pollutants / Q000633:toxicity*; D008168:Lung / Q000187:drug effects* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010126:Ozone / Q000633:toxicity*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010715:Phosphatidylglycerols / Q000378:metabolism; D011312:Pressure; D017433:Protein Structure, Secondary; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry / Q000378:metabolism*
D004785:Environmental Pollutants; D010446:Peptide Fragments; D010715:Phosphatidylglycerols; D037701:Pulmonary Surfactant-Associated Protein B; D015060:1,2-Dipalmitoylphosphatidylcholine; D010126:Ozone; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol