PHA Granule-Associated Proteins and Their Diverse Functions

Abstract

Polyhydroxyalkanoate (PHA) granules are surrounded by an organized protein layer composed of several different granule-associated proteins (GAPs). These include proteins that catalyze PHA polymerization and depolymerization and small proteins known as phasins, the major components of the PHA granule surface. Phasins affect PHA content and the number and size of the granules, but many additional functions have been described for phasins from different PHA producing bacteria. GAPs interact with each other, and some can affect the transcription of PHA associated genes, constituting a complex network that affects polymer synthesis and degradation and contributes to cellular homeostasis. The diverse capabilities of different GAPs have been used for a variety of applications, ranging from protein purification to antigen display and drug delivery.