Objective: To improve the expression level of recombinant human stem cell factor (rhSCF).
Methods: With PCR techniques and synthesized oligonucleotide as primers, the number of nucleotides between the SD sequence and the starting codon ATG of human stem cell factor cDNA was altered, and the preferable codons of E. coli in the N-terminal amino acid sequence were selected.
Results: SDS-PAGE electrophoresis indicated that the ratio of expressed rhSCF to total E. coli proteins increased from 12% to 40% by thermal inducing. With DNA sequencing, the reading frame of the gene was proved to be correct. The sequence of 17 N-terminal amino acids of purified recombinant hSCF has been proved to be identical to the natural hSCF, except the first amino acid-Met.
Conclusions: These studies suggest that the 5'-flanking region of hSCF cDNA plays an important role in its gene expression.