About PHB / Prohibitin:
There are two forms of prohibitin: prohibitin 1 (PHB1) and prohibitin 2 (PHB2). These proteins are ubiquitously expressed and can be found in the nucleus, cytosol and mitochondria of a cell. Of course, these proteins have significant functions (differing depending on their cellular localization) and research suggests that they play a vital role within the mitochondria. This reflects in the fact that you will find that PHB proteins are highly expressed in cells that heavily depend on mitochondrial function.
Within mitochondria, these two proteins will assemble at the inner membrane to form a supra-macromolecular structure. This will then work as a scaffold for proteins and lipids regulating mitochondrial metabolism This scaffold can then play a role in bioenergetics, biogenesis and dynamics, going on to determine the cell fate, death or life.
PHB has been found when researching conditions such as aging, cancer, neurodegenerative diseases, cardiac diseases, kidney diseases and other diseases in which significant mitochondrial impairments have been observed.
PHB1 has a molecular weight of 23kDa and PHB2 has a molecular weight 34 kDa. Both proteins are composed of an N-terminal transmembrane domain that is an evolutionarily conserved prohibitin domain. This domain is common to other scaffold proteins (including stomatin, stomatin-like proteins 1, 2, 3, flotillin, and HflK/C) and a C-terminal coiled-coil domain. This domain is involved in protein–protein interactions, including the interaction between themselves and with transcriptional regulators.
In terms of structure, PHB1 and 2 form a ring-like structure of approximately 1 MDa. This consists of about 12–20 PHB heterodimers, at the mitochondrial inner membrane.