Research Highlight 30th March 2018

Research Highlight 30th March 2018

Structural modelling of the DNAJB6 oligomeric chaperone shows a peptide-binding cleft lined with conserved S/T-residues at the dimer interface.

2018 Mar 26;8(1):5199. doi: 10.1038/s41598-018-23035-9.

Author information

1 MAX IV Laboratory, Lund University, PO Box 118, SE-221 00, Lund, Sweden. christopher.soderberg@ri.se.
2 Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University, PO Box 124, SE-221 00, Lund, Sweden.
3 School of Technology and Health, KTH Royal Institute of Technology and Department of Biosciences and Nutrition, Karolinska Institute, Stockholm, Sweden.
4 School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
5 Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
6 Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University, PO Box 124, SE-221 00, Lund, Sweden. Cecilia.Emanuelsson@biochemistry.lu.se.

Abstract

The remarkably efficient suppression of amyloid fibril formation by the DNAJB6 chaperone is dependent on a set of conserved S/T-residues and an oligomeric structure, features unusual among DNAJ chaperones. We explored the structure of DNAJB6 using a combination of structural methods. Lysine-specific crosslinking mass spectrometry provided distance constraints to select a homology model of the DNAJB6 monomer, which was subsequently used in crosslink-assisted docking to generate a dimer model. A peptide-binding cleft lined with S/T-residues is formed at the monomer-monomer interface. Mixed isotope crosslinking showed that the oligomers are dynamic entities that exchange subunits. The purified protein is well folded, soluble and composed of oligomers with a varying number of subunits according to small-angle X-ray scattering (SAXS). Elongated particles (160 × 120 Å) were detected by electron microscopy and single particle reconstruction resulted in a density map of 20 Å resolution into which the DNAJB6 dimers fit. The structure of the oligomer and the S/T-rich region is of great importance for the understanding of the function of DNAJB6 and how it can bind aggregation-prone peptides and prevent amyloid diseases.

The impact of newly produced protein and dietary fiber rich fractions of yellow pea (Pisum sativum L.) on the structure and mechanical properties of pasta-like sheets.

2018 Apr;106:607-618. doi: 10.1016/j.foodres.2018.01.020. Epub 2018 Jan 12.

Author information

1 Department of Plant Breeding, Swedish University of Agricultural Sciences, Box 101, SE-23053 Alnarp, Sweden.
2 KTH Royal Institute of Technology, School of Chemical Science and Engineering, Fibre and Polymer Technology, SE-100 44 Stockholm, Sweden.
3 MAX-IV Laboratory, Lund University, Box 118, SE-221 00 Lund, Sweden.
4 Department of Food Science, University of Copenhagen, 1958 Frederiksberg C., Denmark.
5 Department of Plant Breeding, Swedish University of Agricultural Sciences, Box 101, SE-23053 Alnarp, Sweden. Electronic address: ramune.kuktaite@slu.se.

Abstract

Two fractions from pea (Pisum sativum L.), protein isolate (PPI) and dietary fiber (PF), were newly produced by extraction-fractionation method and characterized in terms of particle size distribution and structural morphology using SEM. The newly produced PPI and PF fractions were processed into pasta-like sheets with varying protein to fiber ratios (100/0, 90/10, 80/20, 70/30 and 50/50, respectively) using high temperature compression molding. We studied protein polymerization, molecular structure and protein-fiber interactions, as well as mechanical performance and cooking characteristics of processed PPI-PF blends. Bi-modal particle size distribution and chemical composition of the PPI and PF fractions influenced significantly the physicochemical properties of the pasta-like sheets. Polymerization was most pronounced for the 100 PPI, 90/10 and 80/20 PPI-PF samples as studied by SE-HPLC, and polymerization decreased with addition of the PF fraction. The mechanical properties, as strength and extensibility, were likewise the highest for the 100 PPI and 90/10 PPI-PF blends, while the E-modulus was similar for all the studied blends (around 38 MPa). The extensibility decreased with the increasing amount of PF in the blend. The highest amounts of β-sheets were found in the pasta-like sheets with high amounts of PPI (100, 90 and 80%), by FT-IR. An increase in PF fraction in the blend, resulted into the high amounts of unordered structures as observed by FT-IR, as well as in an increase in the molecular scattering distances observed by SAXS. The water uptake increased and cooking loss decreased with increased proportions of the PF fraction, and the consistency of 10 min cooked pasta-like sheets were alike al dente texture. The new knowledge obtained in this study on the use of extraction-fractionation method to produce novel PPI and PF fractions for developing innovative high nutritious food can be of a great importance. The obtained knowledge on the pea protein and fiber processing behaviour could greatly contribute to a better control of functional properties of various temperature-processed products from yellow pea.