- A.J.R. Heck (1)
- R.H.H. Heuvel van den (1)
- G.A. Koningsveld van (1)
- B.J.H. Kuipers (1)
- D. Leys (1)
- H. Mazon (1)
- J. Oost van der (1)
- A.G.J. Voragen (1)
Hydrolysis of Whey Protein Isolate with Bacillus licheniformis Protease: Fractionation and Identification of Aggregating Peptides
Creusot, N.P. ; Gruppen, H. - \ 2007
Journal of Agricultural and Food Chemistry 55 (2007)22. - ISSN 0021-8561 - p. 9241 - 9250.
enzyme-induced gelation - beta-lactoglobulin - limited proteolysis - microstructure - mixtures - alcalase - gels - glu
The objective of this work was to identify the dominant aggregating peptides from a whey protein hydrolysate (degree of hydrolysis of 6.8%) obtained with Bacillus licheniformis protease. The aggregating peptides were fractionated with preparative reversed-phase chromatography and identified with liquid chromatography¿mass spectrometry. The results showed that the dominant aggregating peptide, at pH 7.0, was ß-lg AB [f1¿45]. In addition, the peptides ß-lg AB [f90¿108]-S-S-¿-la [f50¿113], ¿-la [f12¿49]-S-S-¿-la [f50¿113], ß-lg AB [f90¿108]-S-S-ß-lg AB [f90¿108], ß-lg A [f90¿157], and ß-lg AB [f135¿157/158] were also identified as main aggregating peptides. The results further showed that aggregation, via hydrophobic interactions, prevented further digestion (at pH 8.0), thereby explaining the large size of the aggregating peptides. It is hypothesized that B. licheniformis protease breaks down hydrophilic segments in the substrate and, therefore, preserves hydrophobic segments that aggregate once exposed to the solvent
Transcriptional activation by CprK1 is regulated by protein structural changes induced by effector binding and redox state
Mazon, H. ; Gabor, K. ; Leys, D. ; Heck, A.J.R. ; Oost, J. van der; Heuvel, R.H.H. van den - \ 2007
Journal of Biological Chemistry 282 (2007)15. - ISSN 0021-9258 - p. 11281 - 11290.
ionization mass-spectrometry - camp-receptor-protein - desulfitobacterium-dehalogenans - macromolecular complexes - reductive dehalogenase - conformational-changes - limited proteolysis - dna-binding - sp-nov - hafniense
The transcriptional activator CprK1 from Desulfitobacterium-hafniense, a member of the ubiquitous cAMP receptor protein/fumarate nitrate reduction regulatory protein family, activates transcription of genes encoding proteins involved in reductive dehalogenation of chlorinated aromatic compounds. 3-Chloro-4-hydroxyphenylacetate is a known effector for CprK1, which interacts tightly with the protein, and induces binding to a specific DNA sequence ("dehalobox," TTAAT¿-ATTAA) located in the promoter region of chlorophenol reductive dehalogenase genes. Despite the availability of recent x-ray structures of two CprK proteins in distinct states, the mechanism by which CprK1 activates transcription is poorly understood. In the present study, we have investigated the mechanism of CprK1 activation and its effector specificity. By using macromolecular native mass spectrometry and DNA binding assays, analogues of 3-chloro-4-hydroxyphenylacetate that have a halogenated group at the ortho position and a chloride or acetic acid group at the para position were found to be potent effectors for CprK1. By using limited proteolysis it was demonstrated that CprK1 requires a cascade of structural events to interact with dehalobox dsDNA. Upon reduction of the intermolecular disulfide bridge in oxidized CprK1, the protein becomes more dynamic, but this alone is not sufficient for DNA binding. Activation of CprK1 is a typical example of allosteric regulation; the binding of a potent effector molecule to reduced CprK1 induces local changes in the N-terminal effector binding domain, which subsequently may lead to changes in the hinge region and as such to structural changes in the DNA binding domain that are required for specific DNA binding.
Opposite Contributions of Glycinin- and ß-Conglycinin-Derived Peptides to the Aggregation Behavior of Soy Protein Isolate Hydrolysates
Kuipers, B.J.H. ; Koningsveld, G.A. van; Alting, A.C. ; Driehuis, F. ; Voragen, A.G.J. ; Gruppen, H. - \ 2006
Food Biophysics 1 (2006)4. - ISSN 1557-1858 - p. 178 - 188.
heat-induced gelation - soybean proteins - structural characteristics - emulsifying properties - enzymatic-hydrolysis - limited proteolysis - physical-properties - alpha-lactalbumin - gel properties - whey proteins
The aggregation behavior as a function of pH was studied for hydrolysates obtained by hydrolysis of soy protein isolate (SPI) and glycinin- and ß-conglycinin-rich protein fractions with subtilisin Carlsberg. The substrates were hydrolyzed up to degrees of hydrolysis (DH) of 2.2% and 6.5%. Compared with nonhydrolyzed SPI, a decrease in solubility was observed for the hydrolysates of SPI [0.8% (w/v) protein, I¿=¿0.03 M] around neutral pH. At pH 8.0, glycinin hydrolysates had a much lower solubility (~43% and 60%, respectively, for DH 2.2% and 6.5%) than SPI and ß-conglycinin-derived hydrolysates, which were almost completely soluble. Peptides that aggregated were all larger than 5 kDa, and as estimated by size-exclusion chromatography their composition was almost independent of the aggregation pH. The solubility of hydrolysates of SPIs with a varying glycinin and ß-conglycinin composition showed that glycinin-derived peptides are the driving force for the lower solubility of SPI hydrolysates. The solubility of SPI hydrolysates at pH 8.0 was shown not to be the sum of that of glycinin and ß-conglycinin hydrolysates. Assuming that the separate hydrolysis of glycinin and ß-conglycinin did not differ from that in the mixture (SPI), this indicates that ß-conglycinin-derived peptides have the ability to inhibit glycinin-derived peptide aggregation.