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

OSVALDO N. OLIVEIRA JR; FELIPPE J. PAVINATTO; SABINA M. MATÉ; LAURA S. BAKÁS; MARÍA A. DAZA MILLONE; MARÍA E. VELA; VANESA S. HERLAX; ROMINA F. VÁZQUEZ; OSVALDO N. OLIVEIRA JR; FELIPPE J. PAVINATTO; SABINA M. MATÉ; LAURA S. BAKÁS; MARÍA A. DAZA MILLONE; MARÍA E. VELA; VANESA S. HERLAX; ROMINA F. VÁZQUEZ

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

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

0927-7765

Uropathogenic strains of Escherichiacoli produce virulence factors, such as the protein toxin alpha-hemolysin(HlyA), that enable the bacteria to colonize the host and establish aninfection. HlyA is synthetized as a protoxin (ProHlyA) that is transformed intothe active form in the bacterial cytosol by the covalent linkage of two fatty-acylmoieties to the polypeptide chain before the secretion of HlyA into theextracellular medium. The aim of this work was to investigate the effect of thefatty acylation of HlyA on protein conformation and protein-membraneinteractions. Polarization-modulated infrared reflection-absorptionspectroscopy (PM-IRRAS) experiments were performed at the air-water interface, andlipid monolayers mimicking the outer leaflet of red-blood-cell membranes wereused as model systems for the study of protein-membrane interaction. Accordingto surface-pressure measurements, incorporation of the acylated protein intothe lipid films was faster than that of the nonacylated form. PM-IRRASmeasurements revealed that the adsorption of the proteins to the lipidmonolayers induced disorder in the lipid acyl chains and also changed theelastic properties of the films independently of protein acylation. Nosignificant difference was observed between HlyA and ProHlyA in the interactionwith the model lipid monolayers; but when these proteins became adsorbed on abare air-water interface, they adopted different secondary structures. Theassumption of the correct protein conformation at a hydrophobic-hydrophilicinterface could constitute a critical condition for biologic activity.