| Since the advent of penicillin until now,antibiotics have been the first choice drugs for human clinical diseases caused by bacterial infection,and various kinds of antibiotics have been developed one after another.It seems that human beings have a complete solution to these diseases caused by bacterial infection.But that’s not the case.Bacterial infections are still one of the key causes of death among the young,the elderly and those with weakened immune systems.Over the past decades,frequent use of antibiotics and abnormal use of various antibiotics have led to a dramatic increase in the frequency of drug-resistant bacteria worldwide,and even the emergence of key pathogens with antibiotic resistance rates of up to 90% or more have been found in some countries.If one day there are bacteria that are 100 percent resistant to antibiotics,the human situation will be very difficult to imagine,which shows that we need to urgently develop new antibiotics to cope with the possible emergencies in the future.We currently developed most antibiotics were found in a wide range of soil screening of natural products,nothing more than to these antibiotics work approaches are applied to the ribosome,promoting the spin enzyme/cell wall synthesis and DNA topoisomerase these three ways,we have been unable to find a new effective attack targets and ways of antibiotics,and in the past twenty years,because of the lack of specificity and cannot penetrate,outer membrane made by screening and synthetic drug’s effects are very limited.In recent years we have also made some achievements in the development of antibiotics,but the basic are against gram-positive bacteria and gram-negative bacteria development should be on a slow many,mainly due to gram-negative bacteria has a unique mechanism of outer membrane structure,the outer membrane of gram-negative bacteria as long as the lipopolysaccharide of external lobules and internal phospholipids and asymmetric lipid double layer,it can allow small hydrophilic molecules to enter,but larger and hydrophobic molecules cannot pass,the natural barrier can make gram-negative bacteria against many gram-positive bacteria comes easily to the many kinds of antibiotics,At the same time,gram-negative bacteria can also achieve high levels of antibiotic resistance through different genetic mechanisms,including changing or bypassing antibiotic targets,inactivating or destroying antibiotics,or causing mutations in genes encoding up-regulated efflux pumps for multidrug resistance,and so on.In order to protect themselves against gram-negative bacteria,we must avoid the above mentioned targets and pathways of genetic resistance in order to develop new antibiotics against gram-negative bacteria.In order to avoid these pathways while still being effective,we must target the antimicrobial agents of the proteins that are required and exposed to the surface for the processes that occur in the outer membraneIn e.coli,for example,gram-negative bacteria on the surface of the outer membrane biological process mainly has four kinds,synthesis and transport process of phospholipid molecules,respectively,the synthesis of lipopolysaccharide and the transmembrane transport process,lipoprotein transport process and membrane on outer membrane protein folding process,this study selected the way of outer membrane protein folding on film as a research direction.With the help of quality control factors,the outer membrane protein crosses the intima and membrane interstitium to the BAM system to complete the final folding and membrane insertion.Many studies have shown that the BAM system is a necessary system for gram-negative bacteria,and the lack of this system will lead to bacterial death.The two most critical and essential protein subunits BamA and Bam D in the BAM system are the main objects of our study.We developed and designed seven peptides based on the gene sequences of the two protein subunits and in combination with the self-targeting inhibitory short peptide concept of our collaborant professor zhou yao-qi.Self-targeting inhibitory peptides are peptides whose sequences derive from polypeptide fragments of proteins designed to inhibit targets.These peptides are used to inhibit protein-protein interactions or to destroy folded structures.The sequences of the seven short peptides we developed and designed came from parts of the gene sequences of BamA and Bam D proteins respectively.Through a series of experiments,we explored the bactericidal effect and mechanism of the seven peptides,and hoped to select the effective inhibitory peptides through screening and provide experience for the subsequent development of new antibiotics.The following research results have been discovered in this study: 1)Two short peptides with self-targeting inhibitory structure that are very effective in killing Escherichia coli were screened using biochemical methods.2)Experiments using liquid culture confirmed that the two short peptides can inhibit the growth of the flora for 4 hours and 8 hours,respectively.3)After coupling a guide peptide that can specifically penetrate the membrane to one end of the two short peptides by coupling,the two peptides can directly act on E.coli and have a good bactericidal effect.4)The specific detection of the two peptides found that not only can kill E.coli,but also other Gram-negative bacteria similar in structure to E.coli BamA and Bam D.5)Preliminary animal experiments have verified that the two polypeptides also have a certain bactericidal effect on mouse skin.6)Through the study of the mechanism,it is found that the lead peptide damages bacteria by penetrating the membrane.Two peptides will interfere with the normal upper membrane of outer membrane proteins,and one of the peptides will directly interfere with the interaction between BamA and SurA. |
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