Ovalbumin with Glycated Carboxyl Groups Shows Membrane-Damaging Activity.

Ching-Chia Tang,Long-Sen Chang,Ying-Jung Chen,Yi-Jun Shi

doi:10.3390/ijms18030520

Ching-Chia Tang, Long-Sen Chang + Show 2 more

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https://doi.org/10.3390/ijms18030520

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Abstract

The aim of the present study was to investigate whether glycated ovalbumin (OVA) showed novel activity at the lipid-water interface. Mannosylated OVA (Man-OVA) was prepared by modification of the carboxyl groups with p-aminophenyl α-dextro (d)-mannopyranoside. An increase in the number of modified carboxyl groups increased the membrane-damaging activity of Man-OVA on cell membrane-mimicking vesicles, whereas OVA did not induce membrane permeability in the tested phospholipid vesicles. The glycation of carboxyl groups caused a notable change in the gross conformation of OVA. Moreover, owing to their spatial positions, the Trp residues in Man-OVA were more exposed, unlike those in OVA. Fluorescence quenching studies suggested that the Trp residues in Man-OVA were located on the interface binds with the lipid vesicles, and their microenvironment was abundant in positively charged residues. Although OVA and Man-OVA showed a similar binding affinity for lipid vesicles, the lipid-interacting feature of Man-OVA was distinct from that of OVA. Chemical modification studies revealed that Lys and Arg residues, but not Trp residues, played a crucial role in the membrane-damaging activity of Man-OVA. Taken together, our data suggest that glycation of carboxyl groups causes changes in the structural properties and membrane-interacting features of OVA, generating OVA with membrane-perturbing activities at the lipid-water interface.

Highlights

The structure-function relationship of proteins has been extensively studied using chemical modification or site-directed mutagenesis
Previous studies have revealed that bovine serum albumin (BSA) could transfer lipid amphiphile to lipid bilayer membranes [4], suggesting that BSA could interact with lipid bilayers
Previous studies have shown that mannosylated bovine serum albumin (Man-BSA), prepared by the conjugation of carboxyl groups with p-aminophenyl α-D-mannopyranoside, demonstrates membrane-damaging activity [5]

Summary

Introduction

The structure-function relationship of proteins has been extensively studied using chemical modification or site-directed mutagenesis. Modification of lysine residues in Bacillus licheniformis α-amylase changes its substrate specificity [3] These results suggest that chemical modification could improve the biological activities of proteins. BSA does not demonstrate membrane-perturbing activity, mannosylated bovine serum albumin (Man-BSA) prepared by the conjugation of carboxyl groups with p-aminophenyl α-dextro (D)-mannopyranoside, exhibits membrane-damaging activity on the lipid-water interface [5]. These results suggest that protein with a membrane-binding capability can show membrane-perturbing activities after the glycation of its carboxyl groups. To test whether the methodology is common for the preparation of proteins with novel activities on the lipid-water interface, further studies on other proteins with membrane-binding properties might throw more light on this suggestion

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