Cloning and expression of a novel food additive γ-PGA synthase gene

With special molecular structure,γ- poly glutamic acid( γ- PGA) has many characteristics,such as emulsification,thickening,antifreeze and so on. As an additive,γ- PGA can be widely used in food. The gene of pgs BCA were cloned from Bacillus subtilis 115 genome DNA by PCR.Biological information of Pgs BCA were analyzed using the online software( Ex PASy- Prot Param tool,Server 3.0 Signal P,TMHMM Server and Tmpred,PSORTB,Predict Protein,Swiss- Model Workspace) based on the amino acid sequence.As the key enzyme gene of γ- PGA synthesis,expression system of pgs B was constructed.The results showed that the pgs B,pgs C and pgs A genes contained 1182,450,1143 nucleotides and code 393,149,380 amino acids,respectively.Pgs B,Pgs C and Pgs A did not exist signal peptide,belonged to the non secretory protein. The molecular weight of Pgs B,Pgs C and Pgs A were 44016.7,16302.9 and 42759.8 Da,respectively. Pgs B was hydrophilic,unstable acidic protein,its secondary structure was mainly alpha helical,Pgs C protein containing four transmembrane domain,was highly conservative and hydrophobic alkaline membrane binding protein,Pgs A was stable hydrophilic basic protein,which contained one transmembrane region in the N terminal. By SDS- PAGE test,the pgs B gene was expressed successfully and its relative molecular mass was about 45 k Da,was consistent with theoretical value.