Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Translocation of Green Fluorescent Protein to Cyanobacterial Periplasm Using Ice Nucleation Protein: Wipa Chungjatupornchai , Sirirat Fa-aroonsawat; J. Microbiol. 2009;47(2):187-192. Published online May 2, 2009; DOI: https://doi.org/10.1007/s12275-008-0188-x

Abstract: The translocation of proteins to cyanobacterial cell envelope is made complex by the presence of a highly differentiated membrane system. To investigate the protein translocation in cyanobacterium Synechococcus PCC 7942 using the truncated ice nucleation protein (InpNC) from Pseudomonas syringae KCTC 1832, the green fluorescent protein (GFP) was fused in frame to the carboxyl-terminus of InpNC. The fluorescence of GFP was found almost entirely as a halo in the outer regions of cells which appeared to correspond to the periplasm as demonstrated by confocal laser scanning microscopy, however, GFP was not displayed on the outermost cell surface. Western blotting analysis revealed that InpNC-GFP fusion protein was partially degraded. The N-terminal domain of InpNC may be susceptible to protease attack; the remaining C-terminal domain conjugated with GFP lost the ability to direct translocation across outer membrane and to act as a surface display motif. The fluorescence intensity of cells with periplasmic GFP was approximately 6-fold lower than that of cells with cytoplasmic GFP. The successful translocation of the active GFP to the periplasm may provide a potential means to study the property of cyanobacterial periplasmic substances in response to environmental changes in a non-invasive manner.

Stable Expression and Secretion of Polyhydroxybutyrate Depolymerase of Paucimonas lemoignei in Escherichia coli: Se Whan Park , Moon Gyu Chung , Hwa Young Lee , Jeong Yoon Kim , Young Ha Rhee; J. Microbiol. 2008;46(6):662-669. Published online December 24, 2008; DOI: https://doi.org/10.1007/s12275-008-0283-z

Abstract: An efficient strategy for the expression and secretion of extracellular polyhydroxybutyrate depolymerase (PhaZ1) of Paucimonas lemoignei in Escherichia coli was developed by employing the signal peptide of PhaZ1 and a truncated ice nucleation protein anchoring motif (INPNC). Directly synthesized mature form of PhaZ1 was present in the cytoplasm of host cells as inclusion bodies, while a construct containing PhaZ1 and its own N-terminal signal peptide (PrePhaZ1) enabled the secretion of active PhaZ1 into the extracellular medium. However, the PrePhaZ1 construct was harmful to the host cell and resulted in atypical growth and instability of the plasmid during the cultivation. In contrast, INPNC-PhaZ1 and INPNCPrePhaZ1 fusion constructs did not affect growth of host cells. INPNC-PhaZ1 was successfully displayed on the cell surface with its fusion form, but did not retain PhaZ1 activity. In the case of INPNC-PrePhaZ1, the initially synthesized fusion form was separated by precise cleavage of the signal peptide, and active PhaZ1 was consequently released into the culture medium. The amount of PhaZ1 derived from E. coli (INPNC-PrePhaZ1) was almost twice as great as that directly expressed from E. coli (PrePhaZ1), and was predominantly (approximately 85%) located in the periplasm when cultivated at 22°C but was efficiently secreted into the extracellular medium when cultivated at 37°C.

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