Expression of recombinant Human Serum Albumin (rHSA)in E. coli strain BL21 (DE3)

Human serum albumin (HSA) is a multifunctional protein exclusively synthesized by human liver hepatocytes and continuously secreted into the circulation. Escherichia coli, were considered to be one of the efficient platforms for rHSA production due to well-established molecular tools, high growth rate and cultivation capacity. In the present study the coding sequence of HSA gene was codon optimized by Optimizer server and then synthesis and cloned in pET-21 expression vector a by foreign company. The synthesis gene was sequenced to check the T7 promoter and HSA sequences accuracy. This recombinant vector was transformed in E.coli (BL21) and subsequently IPTG was used for induction of recombinant serum albumin protein (rHSA) in E.coli and total protein was assayed by SDS PAG. The SDS-PAG band for rHSA was not seen even after changing in temperature and time for induction. To understand and resolved this problem the coding sequence of HSA was removed from initial recombinant vector by NdeΙ&NotΙ restriction enzymes and subsequently were cloned in 3 bacterial expression vectors (PET-28a, PET-21a and pARA- 28a). The strong SDS-PAG band was seen for E.coli strains that harbor recombinant pET-28a and pARA- 28a with molecular weight almost equal to 66KD and we didn’t seen this result for recombinant PET-21a. The recombinant HSA was purified by Ni-NTA recombinant protein purified kit from Qiagen co. and then evaluated by SDS-PAG. After purification one protein band was seen near to 66KD protein weight marker. Most likely this SDS-PAG band belong to our recombinant HAS.