The Histone Tail Codes
The Histone tails can be thought of as fixed at one end and free to rotate about it's covalent bonds from the fixed end to the last carbon of the free end. Each rotating bond is some function of time. That is to say that from time zero onwards each covalent bond will be at some ramachandran angle...e.g. omega = f(t)). The state of the histone tail at any given time both influences the state of the histone core as well as being influenced by the activity of the histone core. One can therefore examine the complex pattern of the collection of omega functions OR one can simply look at the pattern formed by the last carbon of the free end. Following is one possible code: (0.01,0.0,0.01,1.5,2.5,0.0,1.5,2.5,0.0,1.5,2.5,0.0,1.5,2.5,0.0,1.5,2.5,0.0,1.5,0.01)... and it's resulting image. Note the use of numbers in the ratio of 5/3 ,,,representing the relative rotation rates... and the similarity to Da Vinci's Vitruvian Man..
or from a slightly different angle...
Energy landscape analyses of disordered histone tails reveal special organization of their conformational dynamics.
© 2011 American Chemical Society
- [PubMed - indexed for MEDLINE]
Histone H3 lysine methylation in cognition and intellectual disability disorders
Recent research indicates that epigenetic mechanisms and, in particular, the post-translational modification (PTM) of histones may contribute to memory encoding and storage. Among the dozens of possible histone PTMs, the methylation/demethylation of lysines in the N-terminal tail of histone H3 exhibits particularly strong links with cognitive abilities. First, the persistence and tight association with distinct transcriptional states of the gene make these modifications particularly suitable for being part of the molecular underpinnings of memory storage. Second, correlative evidence indicates that the methylation/demethylation of lysines in histone H3 is actively regulated during memory processes. Third, several enzymes regulating these PTMs are associated with intellectual disability disorders. We review here these three lines of evidence and discuss the potential role of epigenetic mechanisms centered on the methylation of lysine residues on histone H3 in neuroplasticity and neurodevelopmental disorders associated with intellectual disability.
...A number of studies in the last few years have indicated that memory consolidation for a particular task correlates with epigenetic modifications in the nucleus of neurons involved in the acquisition of that memory.
Structures and interactions of the core histone tail domains.
Two Possible Types of Transition Functions
The transition functions for each covalent bond of each histone tail may be either discrete, continuous or combinations of both. As shown in the following table...
Or each bond is described as rotating at some continuous rate described as a function of time. The simplest type in this category would be each rate being some constant. In real life every third covalent bond in proteins is thought to be "fixed". This is not entirely accurate but does describe a possible subset of all the possibilities. So, for example, the bonds would be described as a set of relative angular rates of rotation. e.g. 5 3 0 5 3 0 5 3 0 etc. The possible combinations for even a protein of a few peptides is very large. For a protein of length one and integer rates up to 5 their are 5 times 5 or 25 possibilities. If we allow negative integers to -5 and 0 we have 11 times 11 or 121 possibilities.
The code sequence 0.002,0,0.002,2,1,0,2,1,0,2,4,0,2,4,0.004,2,4,4,0,2,4,0.002,1 yields the following skull like structure...