Physiological Importance of Poly‐(R)‐3‐hydroxybutyrates

Abstract

Poly-(R)-3-hydroxybutyrates (PHB), linear polymers of (R)-3-hydroxybutyrate, are components of all biological cells in which short polymers (<200 monomer residues) are covalently attached to certain proteins and/or noncovalently associated with polyphosphates - inorganic polyphosphate (polyP), RNA, and DNA. The low concentrations, lack of unusual atoms or functional groups, and flexible backbones of this complexed PHB, referred to as cPHB, make them invisible to many analytical procedures; whereas other physical properties - water-insolubility, high intrinsic viscosity, temperature sensitivity, multiple bonding interactions with other molecules - make them requisite participants in vital physiological processes as well as contributors to the development of certain diseases.

New insights in the formation of polyhydroxyalkanoate granules (carbonosomes) and novel functions of poly(3‐hydroxybutyrate)

“…In most cases, translational fusions of potential PGAPs with fluorescent proteins were constructed and co-localized with PHB granules (McCool and Cannon, 1999;Neumann et al, 2008;Ruth et al, 2008;Uchino et al, 2008;2012;Sznajder and Jendrossek, 2011). PHB synthase (PhaC) and phasin (PhaP) of Bacillus megaterium and R. eutropha were the first proteins for which the subcellular localization at the surface of PHB granules was shown by immune-gold labelling in TEM experiments, and/or by fluorescence microscopy using cells with translational fusions of PhaC or PhaP with green fluorescent protein variants (Gerngross et al, 1993;Wieczorek et al, 1995;McCool and Cannon, 1999;Neumann et al, 2008).…”

“…Note the high number of outer membrane proteins. (Schubert et al, 1988;Slater et al, 1988;Peoples and Sinskey, 1989;Gerngross and Martin, 1995;Hiraishi et al, 2005;Peters et al, 2007;Jendrossek, 2009;2012;2013;Cho et al, 2012) phaC2* PHB synthase (gene not expressed)…”

Formation of Polyphosphate by Polyphosphate Kinases and Its Relationship to Poly(3-Hydroxybutyrate) Accumulation in Ralstonia eutropha Strain H16

“…However, it is not known whether PHB and polyP granules are located in the same neighborhood simply because of limited space in the cell or whether there is a physical connection either between the two polymers or between the two polymers and a third common compound, such as the bacterial nucleoid. A physical connection of polyP with low-molecularweight oligo(PHB) is well-known for Ca-polyP-PHB complexes (nonstorage PHBs) in biological membranes of E. coli (23)(24)(25)(26)(27). Remarkably, a physiological connection of PHB metabolism with the formation of polyP granules has also been known for a long time.…”

PhaM Is the Physiological Activator of Poly(3-Hydroxybutyrate) (PHB) Synthase (PhaC1) in Ralstonia eutropha

“…PHAs are meanwhile commercially available products, e.g., as packaging materials, but, remarkably, the use of PHAs as high-technology materials in the medical field has also made considerable progress (5). PHB in vivo plays also a role in form of PHB-calcium-polyphosphate complexes (6,7), and recently it was shown that PHBylation of channel protein TRPM8 modulates channel function in mammalian cells (8). This work focuses on the function of PHB as a storage compound in the model organism of PHB research, Ralstonia eutropha H16 (9).…”