Palmitoylation of lung surfactant protein SP-C alters surface thermodynamics, but not protein secondary structure or orientation in 1,2-dipalmitoylphosphatidylcholine langmuir films.
Pulmonary surfactant-specific protein, SP-C, isolated from porcine lung lavage, has been deacylated to investigate the role of the two thioester linked palmitoyl chains located near the N-terminus. Surface thermodynamic properties, secondary structure, and orientation of native and deacylated SP-C in 1, 2-dipalmitoylphosphatidylcholine (DPPC) monolayers has been characterized by combined surface pressure-molecular area (pi-A) isotherms and infrared reflection-absorption spectroscopy (IRRAS) measurements. The isotherms indicate that deacylation of SP-C produces more fluid monolayers at pressures less than 30 mN m-1. The helical secondary structure and tilt angle (70-80 degrees relative to the surface normal) of SP-C remained essentially unchanged upon deacylation in DPPC monolayers at a surface pressure approximately 30 mN m-1. The results are consistent with a model that acylation of SP-C may influence the rapid protein-aided spreading of a surface-associated surfactant reservoir, but not the structure of DPPC or SP-C in the monolayer at higher surface pressures.
Flach
C R
CR
Department of Chemistry, Rutgers University, Newark, NJ 07102, USA. flach@andromeda.rutgers.edu
Gericke
A
A
Keough
K M
KM
Mendelsohn
R
R
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011510:Proteolipids / Q000737:chemistry*; D011663:Pulmonary Surfactants / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D011510:Proteolipids; D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine