Signal sequence and alanine-rich region of streptococcal protein antigen A of Streptococcus sobrinus can direct localization of alkaline phosphatase to the periplasm of Escherichia coli

Abstract

Streptococcal protein antigen A (SpaA) of Streptococcus sobrinus is expressed on the surface of cells and extracellularly. TnphoA which lacks signals for transcription and membrane transport of Escherichia coli alkaline phosphatase was used to analyze the sequences necessary for transport of a SpaA/PhoA fusion protein across the cytoplasmic membrane to the periplasm of E. coli cells. Of 15 alkaline phosphataseproducing isolates analyzed, all were found to localize more than 85% of the SpaA/PhoA hybrid protein to the periplasm of E. coli cells. From DNA sequence analysis, all were found to have TnphoA inserted into an identical site. The insertion site of TnphoA was downstream from the coding sequence that generates four tandemly repeated alanine-rich sequences of 82 amino acid residues. These results suggest that in addition to the signal sequence, mature protein sequences containing alanine-rich repeat sequences may play a role in the export of the SpaA protein across a bacterial membrane. ß

Permeability enhancement of Escherichia coli by single‐walled carbon nanotube treatment

“…6,7 One may employ signal sequence to avoid the complete spillage of cellular contents by translocating the product either to the periplasm or the culture fluid since these compartments are less populated with biological materials derived from the host. [8][9][10] Indeed, specific examples exist where osmotic shock or the direct processing of cell-free culture supernatant led to cleaner products. [11][12][13] Alternatively, the properties of carbon nanotubes show potential to aid in bioseparation applications.…”

“…Treatment by lysozyme when additional proteinaceous material can be tolerated, or French Press are popular means . One may employ signal sequence to avoid the complete spillage of cellular contents by translocating the product either to the periplasm or the culture fluid since these compartments are less populated with biological materials derived from the host . Indeed, specific examples exist where osmotic shock or the direct processing of cell‐free culture supernatant led to cleaner products …”