The Ulrich Hartl team in Germany reveals the mechanism by which HSP70 assists in the folding of heat-sensitive proteins.

On July 30, 2019, the Ulrich Hartl team of the Max Planck Institute for Biochemistry in Germany (first author Dr. Zhao Wei) published an article entitled The Hsp70 Chaperone System Stabils a Thermo Subpteeome in E. Coli in cell Reports, revealing how Hsp70 assists in the folding mechanism of a class of heat-sensitive proteins.
in the study, researchers used quantitative proteomics (stabilized isotope amino acid culture spout marks, SILAC) to explore the structural stability of the cytoplasmic protein group in combination with limitproteolysis (pulse proteolysis, PP) (see Figure 1).
specific process is: first, in the rapid lysis of protoplasm (walled E. coli cells) at the same time, add the cutting activity of the more active thermolysine protease (thermolysin) deenzymely de-folded protein, processing for 1 minute, at the same time, with no thermophile protease treatment of the protoplasm lysate as a comparison;
the folding content of protein scanted by mass spectrometry.
in different cell growth states, the study identified about 2,400 cell plasma proteins of 1500, the main findings are the following: 1. In normal physiological conditions, there are nearly 500 proteins (about 25% of the total protein volume) in dynamic structure; In the state of heat stimulation, about 33% of the total protein is cut by thermophile protease enzymes, of which about 200 thermal proteins have structural changes and defolding, exposing hydrophobic peptide segments.
these hydrophobic peptide segments were originally buried inside the protein structure (see Figure 3, Extension Factor G and UvrABC System Protein UvrA).
these thermal proteins are characterized by relatively large molecular masses, heteropolymer complexes, and c.37 protein folding structures.
some of the necessary proteins fold down the heat stimulation, causing the cell to grow slower (e.g. extending factor G).
highly expressed Hsp70, which promotes the folding or defolding of many thermosensitive proteins, including c.37 folding structures and ribosome proteins ( see Figure 2), even withthermal mechanical conditions.
its specific mechanism has yet to be studied.
3. c.37 folding structure is the oldest folding structure in evolution and is widely found in nucleotide enzymes.
c.37 proteins are often versatile and the protein composition changes during interaction with nucleotides.
in addition, the folding of the alpha/beta topology of c.37 often requires long-distance amino acid sequence interactions and is prone to unstable folding intermediates.
these findings suggest that the Hsp70 family has evolved in tintation with the optimization of protein folding and its function.
4. DnaK protects a lot of ribosome proteins at high temperatures and maintains the integrity of ribosomes.
most ribosome proteins have positive charge in normal physiological conditions, and based on these results, the authors speculate that in order to fold the highly conservative ribosome proteins, the Hsp70 family has evolved binding specificity to the positively charged and hydrophobic amino acid sequence.
this specificity largely determines the pattern of interaction between Hsp70 and protein substrates.
5. Molecular companion is a "double-edged sword" and high-expression DNAK also causes a small amount of protein to fold.
these proteins tend to have smaller molecular masses and monomer proteins (Figure 2), such as septum site-on-protein minD (see Figure 3) and RNA polymerase factor RpoH.
Hsp70 affects rpoH folding, which regulates the heat shock reaction and affects the expression of the heat shock gene.
, Hsp70 plays an important role in maintaining the structural stability and function of a class of heat-sensitive proteins.
study has revealed the need to strictly control the level of expression of molecular companion proteins in cells to accommodate optimal cell growth.
can continue to study the relationship between molecular companion proteins and protein folding, especially during aging, to help understand the pathogenesis of neurodegenerative diseases or folding diseases.
study background protein folding is a major biological problem that has not been solved by the central law of molecular biology.
in order to perform its function, the protein is in a dynamic balance of folding and defolding.
under pressure, such as heat stimulation, many proteins become degenerative and lose protein activity. Abnormal folding of
proteins can cause protein aggregation and even precipitation, disrupting cell stability, and thus causing neurodegenerative and related diseases.
the protein volume control system (molecular companion protein and protein degradation machine) in the cell, the folding of the protein group within the cell is monitored at all times.
molecular companion protein is a class of proteins that assist in the folding and assembly of proteins within cells.
the heat shock protein 70 family (hsp70 family), is a class of molecules about 70 Kda and highly conservative, including DNAK in E. coli. The main function of the
Hsp70 is to combine the hydrophobic zone of the unfolded polypeptide chain in the form of ATP dependence, which is then helped to fold with controlled release.
so far, the folding state of intracellular proteomics has not been reported.
, how many proteins in the cell are protein-degeneration (thermal proteins)) in a heat-stimulating state? What are the characteristics of these heat-sensitive proteins? How does molecular companion protein help with these thermal proteins? These fundamental issues need further study.
Source: BioArt.