Search results for " folding"
showing 10 items of 226 documents
(DIS)Assembly and Structural Stability of mtHsp60 and its Precursor NaÏve Form
2015
Heat shock protein 60kDa is a molecular chaperone (GroEL human homolog) that assists protein folding in mitochondria (mtHsp60). It is synthesized in the cell cytoplasm as a higher molecular weight precursor form (p-mtHsp60) containing a N-terminal targeting sequence, that is cleaved after import into the mitochondrial matrix [1, 2].It has been established, and demonstrated by various techniques, Hsp60 can accumulate in the cytosol, in various pathological conditions (i.e., cancer and chronic inflammatory diseases). The cytosolical Hsp60 accumulation mechanism may occur with or without mitochondrial release concomitantly, so that in the cytosol the two types of 60 kDa chaperonin proteins, (m…
Acquisition of Structure-guiding and Structure-forming Properties during Maturation from the Pro-silicatein to the Silicatein Form
2012
Silicateins are the key enzymes involved in the enzymatic polycondensation of the inorganic scaffold of the skeletal elements of the siliceous sponges, the spicules. The gene encoding pro-silicatein is inserted into the pCold TF vector, comprising the gene for the bacterial trigger factor. This hybrid gene is expressed in Escherichia coli and the synthesized fusion protein is purified. The fusion protein is split into the single proteins with thrombin by cleavage of the linker sequence present between the two proteins. At 23 °C, the 87 kDa trigger factor-pro-silicatein fusion protein is cleaved to the 51 kDa trigger factor and the 35 kDa pro-silicatein. The cleavage process proceeds and res…
Atomic Structures of Two Novel Immunoglobulin-like Domain Pairs in the Actin Cross-linking Protein Filamin
2009
Filamins are actin filament cross-linking proteins composed of an N-terminal actin-binding domain and 24 immunoglobulin-like domains (IgFLNs). Filamins interact with numerous proteins, including the cytoplasmic domains of plasma membrane signaling and cell adhesion receptors. Thereby filamins mechanically and functionally link the cell membrane to the cytoskeleton. Most of the interactions have been mapped to the C-terminal IgFLNs 16–24. Similarly, as with the previously known compact domain pair of IgFLNa20–21, the two-domain fragments IgFLNa16–17 and IgFLNa18–19 were more compact in small angle x-ray scattering analysis than would be expected for two independent domains. Solution state NM…
Clusterization and strong coupled-channels effects in deuteron interaction with $^9$Be nuclei
2019
Angular distributions of protons, deuterons, tritons and alpha particles emitted in the d + alt;supagt;9alt;/supagt;Be reaction at Ealt;subagt;labalt;/subagt;=19.5 and 35.0 MeV have been measured.a#13; The elastic scattering channel is analysed in the framework of both the Optical Model and the Coupled-Channel approach. a#13; The interaction potential of the alt;iagt;dalt;/iagt; + alt;supagt;9alt;/supagt;Be system is calculated in the framework of the Double-Folding model using the α+α+alt;iagt;nalt;/iagt; three-body wave function of the alt;supagt;9alt;/supagt;Be nucleus.a#13; The (alt;iagt;dalt;/iagt;,alt;iagt;palt;/iagt;) and (alt;iagt;dalt;/iagt;,alt;iagt;talt;/iagt;) one-nucleon-transf…
Simulations and Experiments in Protein Folding
2014
The interplay between simulations and experiments of protein folding has largely contributed to the elucidation of many important aspects of the phenomenon. In this chapter, I briefly describe the experiments which provide information on the kinetics of the protein folding process, and help to characterize the folding transition state. Then, I show how to probe the kinetics of protein folding using molecular dynamics simulations, how to compare the simulations with the experiments and how to help and rationalize the latter, ultimately offering a molecular picture of the process. After the production of suitable molecular dynamics simulation data in the form of trajectories, the procedure in…
All-or-none proteinlike folding transition of a flexible homopolymer chain.
2009
Here we report a first-order all-or-none transition from an expanded coil to a compact crystallite for a flexible polymer chain. Wang-Landau sampling is used to construct the complete density of states for square-well chains up to length 256. Analysis within both the microcanonical and canonical ensembles shows a direct freezing transition for finite length chains with sufficiently short-range interactions. This type of transition is a distinctive feature of "one-step" protein folding and our findings demonstrate that a simple homopolymer model can exhibit protein-folding thermodynamics.
The tetrameric α-helical membrane protein GlpF unfolds via a dimeric folding intermediate.
2011
Many membrane proteins appear to be present and functional in higher-order oligomeric states. While few studies have analyzed the thermodynamic stability of α-helical transmembrane (TM) proteins under equilibrium conditions in the past, oligomerization of larger polytopic monomers has essentially not yet been studied. However, it is vital to study the folding of oligomeric membrane proteins to improve our understanding of the general mechanisms and pathways of TM protein folding. To investigate the folding and stability of the aquaglyceroporin GlpF from Escherichia coli, unfolding of the protein in mixed micelles was monitored by steady-state fluorescence and circular dichroism spectroscopy…
Structural stability and properties of three isoforms of the major light-harvesting chlorophyll a/b complexes of photosystem II.
2008
AbstractThree isoforms of the major light-harvesting chlorophyll (Chl) a/b complexs of photosystem II (LHCIIb) in the pea, namely, Lhcb1, Lhcb2, and Lhcb3, were obtained by overexpression of apoprotein in Escherichia coli and by successfully refolding these isoforms with thylakoid pigments in vitro. The sequences of the protein, pigment stoichiometries, spectroscopic characteristics, thermo- and photostabilities of different isoforms were analysed. Comparison of their spectroscopic properties and structural stabilities revealed that Lhcb3 differed strongly from Lhcb1 and Lhcb2 in both respects. It showed the lowest Qy transition energy, with its reddest absorption about 2 nm red-shifted, an…
CO rebinding kinetics and molecular dynamics simulations highlight dynamic regulation of internal cavities in human cytoglobin
2013
Abstract: Cytoglobin (Cygb) was recently discovered in the human genome and localized in different tissues. It was suggested to play tissue-specific protective roles, spanning from scavenging of reactive oxygen species in neurons to supplying oxygen to enzymes in fibroblasts. To shed light on the functioning of such versatile machinery, we have studied the processes supporting transport of gaseous heme ligands in Cygb. Carbon monoxide rebinding shows a complex kinetic pattern with several distinct reaction intermediates, reflecting rebinding from temporary docking sites, second order recombination, and formation (and dissociation) of a bis-histidyl heme hexacoordinated reaction intermediate…
Hsp90 dictates viral sequence space by balancing the evolutionary tradeoffs between protein stability, aggregation and translation rate
2017
AbstractAcquisition of mutations is central to evolution but the detrimental effects of most mutations on protein folding and stability limit protein evolvability. Molecular chaperones, which suppress aggregation and facilitate polypeptide folding, are proposed to promote sequence diversification by buffering destabilizing mutations. However, whether and how chaperones directly control protein evolution remains poorly understood. Here, we examine the effect of reducing the activity of the key eukaryotic chaperone Hsp90 on poliovirus evolution. Contrary to predictions of a buffering model, inhibiting Hsp90 increases population sequence diversity and promotes accumulation of mutations reducin…