Raman study of the puroindoline-a/lysopamitoylphosphatidylcholine interaction in free standing black films

Role of non-prolamin proteins and low molecular weight redox agents in protein folding and polymerization in wheat grains and influence on baking quality parameters

The various enzyme systems and low molecular weight (LMW) redox agents are related to the folding and polymerization of prolamins in the ripening wheat grains and the formation of baking quality. Protein disulfide isomerases (PDIs) and cyclophylins accelerate "correct" folding of prolamins, which is most likely necessary for the subsequent formation of the macromolecular structure of the gluten protein matrix. PDIs are also involved in the polymerization of prolamins, catalyzing the oxidation of protein sulfhydryl groups. Molecular chaperone binding BiP protein facilitates folding of prolamins, with its role increasing in the stressful conditions. Reducing systems of thioredoxin and glutaredoxin, LMW redox pairs GSH/GSSG and Asc/DHAsc, thiol oxidases, and lipoxygenases (LOXs) regulate redox balance and the rate of polymerization of prolamins at the different stages of grain ripening. Additionally, LOX is probably involved in the protein-starch-lipid interactions between the starch granule and the protein matrix, mediated by puroindolines, determining the formation of grain texture. It is assumed that the high variability of baking quality in different environmental conditions is due to the interaction of labile enzyme systems with the storage proteins in the developing wheat caryopsis.

Expression, purification and antimicrobial activity of puroindoline A protein and its mutants

Wheat puroindoline proteins, PINA and PINB, play key roles in determining wheat grain hardness as well as in defending the plant against pathogens. PINA has much greater membrane-binding property and antimicrobial activity because it contains more tryptophan residues in the unique tryptophan-rich domain (TRD). In order to obtain proteins with higher antimicrobial activity, mutants of PINA containing two or three copies of TRD, designated ABBC and ABBBC, respectively, were constructed and expressed in E. coli Rosetta-gami (DE3). Metal affinity chromatography was used to purify the soluble affinity-tagged recombinant proteins. The secondary structures of the recombinant proteins were predicted by the online program Protein Homology/analog Y Recognition Engine v2.0 and experimentally assessed using circular dichroism. Minimum inhibition concentration tests and fluorescence microscope analyses were employed to evaluate the antimicrobial activities of the mutants. The results showed that the purified recombinant ABBC was correctly folded and presented significantly higher antimicrobial activities against E. coli and S. aureus than wild-type PINA, suggesting its potential use as an antimicrobial agent. The results also confirmed that TRD is a determinant of the antimicrobial activity of PINA and demonstrated that it is feasible to enhance the antimicrobial activity of PINA by adding one copy of TRD.