Interaction of acylated and unacylated forms of E. coli alpha-hemolysin with lipid monolayers: a PM-IRRAS study

ROMINA VAZQUEZ; ANTONIETA DAZA-MILLONE; FELIPPE PAVINATTO; VANESA HERLAX; LAURA BAKÁS; OSVALDO OLIVEIRA JR; M. ELENA VELA; SABINA MATÉ

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 158 p. 76 - 83

0927-7765

Uropathogenic strains of Escherichia coli produce virulence factors, such as the protein toxin alpha-hemolysin (HlyA), that enable the bacteria to colonize the host and establish an infection. HlyA is synthetized as a protoxin (ProHlyA) that is transformed into the active form in the bacterial cytosol by the covalent linkage of two fatty acyl moieties to the polypeptide chain prior to its secretion into the extracellular medium. The aim of this work was to investigate the effect of fatty acylation of HlyA on protein conformation and protein-membrane interactions. Polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) experiments were performed at the air-water interface, and lipid monolayers mimicking the outer leaflet of red blood cell membranes were used as model systems for protein-membrane interactions studies. According to surface pressure measurements, incorporation of the acylated protein into the lipid films was faster. PM-IRRAS measurements revealed that the adsorption of the proteins to the lipid monolayers induced disorder in the lipid acyl chains, also changing the elastic properties of the films independently of protein-fatty acylation. No significant difference was observed between HlyA and ProHlyA in the interaction with the lipid monolayers mimicking a cell membrane, but when these proteins adsorbed on a bare air-water interface they adopted different secondary structures. These differences in protein conformation at a hydrophobic-hydrophilic interface could be a critical factor for biological activity.