Vol.:(0123456789) 1 3 International Journal of Peptide Research and Therapeutics https://doi.org/10.1007/s10989-018-9709-6 Optimization of Human Serum Albumin Periplasmic Localization in Escherichia coli Using In Silico Evaluation of Diferent Signal Peptides Mohammad Hassan Jahandar 1  · Ali Forouharmehr 2 Accepted: 13 April 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Signal peptides (SPs) are essential tools to keep folding and function of recombinant proteins which are folded by disulfde bonds. Human serum albumin (HSA) is a protein with medical application which is folded by 17 disulfde bonds. Therefore, the production of this protein as recombinant protein needs appropriate SP. This study was performed to identify the best SP to express HSA in Escherichia coli. At frst, 42 signal sequences (SSs) were collected from the database, then SP probability and SP regions were predicted by SignalP (version 4). Physico-chemical features of SPs were also evaluated by Portparam, whereas signal solubility was assessed by SOLpro. Finally secretion sorting of SPs were investigated by PRED-TAT server. The results of this study revealed that, among 42 signal sequences, FlgI, DsbG, OmpC and MepA (respectively) are theoreti- cally the best SPs to express HSA in E. coli. Keywords Human serum albumin · Signal peptide · E. coli · Bioinformatics Introduction Human serum albumin (HSA) is one of the most abun- dant proteins in serum and plasma which is released by liver cells. Molecular mass of this protein is 67.25 kDa with 591 amino acids and it has three domains which are folded by 17 disulfde bonds. Half-life of HAS is around 20 days and has an important role in the adjustment of blood osmatic pressure. These features of HSA are considered, to apply this protein as therapeutic molecule for the treatment of patients with burn injuries (Colmenarejo 2003; Leich et al. 2007; Peters Jr 1995; Rosenoer et al. 2014). For this purpose, nowadays, HSA is being produced through blood plasma extraction, moreover, this method is too expensive and also increases the risk of pathogenic pollutions. There- fore, the production of HSA as recombinant protein can be an appropriate alternative for the currently used methods. HSA is a simple protein which does not need post transla- tion modifcation; hence, this protein (as a recombinant protein) can be easily expressed in prokaryote expression system like Escherichia coli (Peters Jr 1995). Although prokaryote expression system is simple and afordable in expressing recombinant proteins, this system requires some considerations such as maintaining disulfde bonds (Ali et al. 2017). As matter of fact, in order to maintain disulfide bonds and recombinant protein folding, they must be directed to periplasm compartment of Bacteria, because this compartment, in contrast to cytoplasm, can provide reductive condition to save disulfde bonds and consequently to fold the recombinant proteins. To direct a nascent recombinant protein to periplasm compartment, a signal peptide (SP) is required (Ali et al. 2017). In fact, SP is an amino acid sequence in the N-terminal of nascent proteins with three important regions including: n, h and c regions (respectively) (Ali et al. 2017; Manica et al. 2017). n Region has positive charge that helps it to interact with the membrane of periplasm compartment; h region usually has hydrophobic features and is important in translocation of nascent proteins across membrane between cytoplasm and periplasm; whereas c region helps SP to be cleaved from recombinant protein (Ali et al. 2017; Zamani et al. 2015). Although SPs play an important role in expressing recombinant protein, unfortunately there is no universal * Mohammad Hassan Jahandar Jahandar@iaubam.ac.ir Ali Forouharmehr Forouharmehr@gmail.com 1 Department of Agriculture, Bam Branch, Islamic Azad University, Bam, Iran 2 Department of Animal Science, Faculty of Agriculture, Lorestan University, Khorramabad, Iran