Character Of The Single-Stranded DNA Protein From Thermus TC16 And Its Structure Entropy Distribution

Single-stranded DNA-binding protein(SSB)can bind to single-stranded regions of DNA to prevent premature annealing,to protect the single-stranded DNA from being digested by nucleases,and to allow other enzymes to function effectively upon it.SSB plays an important role in DNA metabolism:replication,recombination and repair.Thermus TC16 Single-stranded DNA-binding protein(TSB)gene tsb was amplified and sequenced.tsb had 810bp and the GC content was 60%.Bioinformatics analysis showed TSB had two oligonucleotide/ribose binding fold area,OBF1(at 9-105aa)and OBF2(at 131-227aa).In order to investigate their functions,tsb,OBF1 and OBF2 were cloned,expressed and characterized.The result showed that only TSB and OBF2 expression protein TOR2 could bind Single-stranded DNA.Proteins heat-resistant level has a certain relationship to their structural entropy.In order to analyze the thermal stability strategy of TSB,structural entropy of SSB from thermophilic strainThermus and mesophilic strain E.coli was compared,particularly focusing on the structure entropy distribution in and around the functional residues.According to the structure entropy analysis,we proposed the protein thermostable strategy.First,avoid long region of high/low structure entropy distribution in the proteins entropy plate.Second,if the functional residue sites have high structural entropy,surrounding them by low structure entropy of the residues would help to maintain thermostability.Finely,if functional residue sites have low structural entropy,surrounded by some relatively high structural entropy residues could help to maintain its thermostability.Based strategies mentioned above,we proposed the principles for improvement protein thermostability:a long region of high/low structural the entropy plate will be avoided;If the structure entropy of the functional residues is too high,then add low structure entropy residues surrounding them;To keep thermostabiliy and activity,structure entropy of residues not simply related low structural entropy,wavy distribution of the high and low structural entropy maybe represent the life rhythm.