A phasin with extra talents: a polyhydroxyalkanoate granule-associated protein has chaperone activity

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Phasins are proteins associated with polyhydroxyalkanoate granules.
• A phasin (PhaPAz) from Azotobacter sp FA-8 showed growth-promoting and stress-protecting effects in E. coli.
• This suggested potential chaperone-like activities of PhaPAz.

Purpose of the Study:

• To investigate the chaperone-like activities of PhaPAz in vitro and in vivo.
• To determine the subcellular localization of PhaPAz in E. coli.
• To explore the role of PhaPAz in protein folding and aggregation within E. coli.

Main Methods:

• In vitro assays using citrate synthase to assess thermal aggregation and refolding.
• Microscopy techniques to analyze PhaPAz subcellular localization in E. coli.
• Coexpression studies of PhaPAz with an aggregation-prone protein (PD) in E. coli.

Main Results:

• PhaPAz prevented in vitro thermal aggregation of citrate synthase.
• PhaPAz facilitated citrate synthase refolding after chemical denaturation.
• PhaPAz colocalized with PD inclusion bodies, and its coexpression reduced inclusion body formation.

Conclusions:

• PhaPAz exhibits significant chaperone-like functions in vitro and in vivo in E. coli.
• Phasins may possess a general protective role in natural polyhydroxyalkanoate-producing bacteria.
• This study expands the known functions of phasins beyond polyhydroxyalkanoate granule association.