Tetrameric proteins
A tetrameric protein is a protein that is composed of four subunits. It can be divided into homotetramers , in which all protein subunits are identical (for example, glutathione S-transferase or single-strand binding proteins ), dimers of heterodimers (such as hemoglobin ), and heterotetramers , in which all subunits are different from one another.
Interactions of the subunits in tetrameric proteins
The interactions between the subunits of tetrameric proteins are mostly of a non- covalent nature, primarily hydrophobic effects , hydrogen bonds and electrostatic interactions. In the case of proteins such as sorbitol dehydrogenase (SDH), an evolutionary development from a monomer via a dimer to today's tetramer is assumed. The binding of the subunits in tetrameric proteins is driven by a gain in Gibbs energy , which can be calculated using the dissociation constant . This combination of four subunits A, B, C and D is shown in the following figure using the example of SDH:
Hydrogen bonds between subunits
Networks of hydrogen bonds between subunits have proven to be important for the stability of the quaternary structure . This was illustrated in a study on (mammalian) SDH using sequence and structure comparisons, energy calculations, gel filtration and enzyme kinetics.
Individual evidence
- ↑ a b c M. Hellgren, C. Kaiser, S. de Haij, A. Norberg, JO Höög: A hydrogen-bonding network in mammalian sorbitol dehydrogenase stabilizes the tetrameric state and is essential for the catalytic power. . In: Cell. Mol. Life Sci. (CMLS) . 64, No. 23, 2007, pp. 3129-3138. doi : 10.1007 / s00018-007-7318-1 . PMID 17952367 .