Exploring the influence of phospholipid monolayer conformation and environmental conditions on the interfacial binding of Gibberella Zeae lipase.

Abstract

The involvement of different parameters on Gibberella zeae lipase (GZEL) membrane binding were characterized by using monomolecular film technology and circular dichroism spectroscopy. Among four kinds of phospholipid monolayers, 1,2‑dimyristoyl‑sn‑glycero‑3‑phosphoethanolamine have the highest maximum insertion pressure (MIP) value. Comparing the GZEL adsorption to phosphatidylcholine monolayers with different acyl chains in sn-1 and sn-2 positions, the higher MIP values were found for 1,2‑dilauroyl‑sn‑glycero‑3‑phosphocholine. Significantly improvement between 1,2‑dioleoyl‑sn‑glycero‑3‑phosphocholine and 1,2‑distearoyl‑sn‑glycero‑3‑phosphocholine suggested that the presence of fatty acid unsaturation may affect protein adsorption by changing the chemical structure in each phospholipid. The MIP value was shown higher (48.6 mN m-1) at pH 5 and pH 6 (47.5 ± 1.9 mN m-1) but decreased significantly (34.2 mN m-1) at pH 9. This may indicate that the proportion of helices in the protein decreases with the alteration of the catalytic center, thus affecting the binding of the protein to its substrate. The MIP values obviously decreased with increasing salt ion concentration, suggesting that excessive salt ion concentration may destabilize the secondary and tertiary structures of the protein, thereby affecting the characteristics of its adsorption at the interfaces. Present studies improve our understanding on the protein-membrane interaction of this enzyme.