Tail domains

Zheng C, Hayes JJ (2003) Structures and interactions of the core histone tail domains. Biopolymers 68 539-546... 

The histone variants of H2A form the largest family of identified histone variants (Redon et al, 2002 Sarma and Reinberg, 2005). This could be associated with both the strategic position that has the histone H2A within the histone octamer and the less stable interaction of the H2A-H2B dimmer with both DNA and the (H3-H4)2 tetramer within the nucleosome (Luger et al, 1997). Most of the histone H2A variants exhibit a unique property in addition to the N-terminal tail domain, they also posses an unstructured C-terminal tail. To date four variants of histone H2A have been discovered. These include, H2AZ, H2A.X, macroH2A and H2A.Bbd. The highest differences in the primary structure of these H2A variants are observed in their C-terminal portion. Each of these variants could be efficiently incorporated in the nucleosome in vitro and in vivo. The presence of these variants alter the structural and functional properties of the nucleosome distinctly. 

Figure 5 Structure of the archaeai GatDE aminoacyi-tRNA amidotransferase. GatDE forms a heterotetramer, with two GatDE proteins binding through their GatD subunits. Binding of tRNA° " induces a conformational shift of the helical and tail domains, which scan the D-ioop and the T-arm. This figure was reproduced from H. Oshikane K. Sheppard S. Fukai ...

Although the histone fold was first described from the structure of the histone octamer core of the nucleosome [17], the high a-helical content was predicted much earlier [43]. The core histones possess three functional domains (1) the histone fold domain, (2) an N-terminal tail domain, and (3) various accessory helices and less structured regions. The N-terminal tail domains of the core histones are currently the focus of intense research. Covalent modifications of residues in these unstructured domains appear to modify local chromatin structure, either directly or... 

Angelov, D., Vitolo, J.M., Mutskov, V., Dimitrov, S., and Hayes, J.J. (2001) Preferential interaction of the core histone tail domains with linker DNA. Proc. Natl. Acad. Sci. USA 98, 6599-6604. Tobias, I., Coleman, B.D., and Olson, W. (1994) The dependence of DNA tertiary structure on end conditions theory and implications for topological transitions. J. Chem. Phys. 101, 10990-10996. Coleman, B.D., Tobias, I., and Swigon, D. (1995) Theory of the influence of end conditions on selfcontact in DNA loops. J. Chem. Phys. 103, 9101-9109. 

Histone methylation was first reported in 1964 [118], Core histones H2B, H3, and H4 are modified by methylation (Fig. 1). H3 and H4 are modified at lysines and arginines located primarily in the N-terminal tail. Histone methylation does change the charge of the protein at physiological pH. However, methylation does increase the hydrophobicity of the lysine residue and reduces its ability to form hydrogen bonds [119]. The sites of methylation (Lys-20 in H4 and Lys-27 in H3) are positioned at the boundary between the very basic N-terminal tail domain and the more hydrophobic sequence of the remainder of the molecule. Lys-20 of histone H4 is also in the basic region that binds to nucleosomal DNA [120]. Methylation at these sites may alter nucleosome structure [121,122]. 

Fig. 1. Histone modifications on the nucleosome core particle. The nucleosome core particle showing 6 of the 8 core histone N-terminal tail domains and 2 C-terminal tails. Sites of post-translational modification are indicated by coloured symbols that are defined in the key (lower left) acK = acetyl lysine, meR = methyl arginine, mcK = methyl lysine, PS = phosphoryl serine, and uK = ubiquitinated lysine. Residue numbers are shown for each modification. Note that H3 lysine 9 can be either acetylated or methylated. The C-terminal tail domains of one H2A molecule and one H2B molecule are shown (dashed lines) with sites of ubiquitination at H2A lysine 119 (most common in mammals) and H2B lysine 123 (most common in yeast). Modifications are shown on only one of the two copies of histones H3 and H4 and only one tail is shown for H2A and H2B. Sites marked by green arrows are susceptible to cutting by trypsin in intact nucleosomes. Note that the cartoon is a compendium of data from various organisms, some of which may lack particular modifications e.g., there is no H3meK9 in S. cerevisiae. (From Ref [7].)...

Figure 4 SAXS-based model of CBH II (redrawn from ref. 31 with permission) Note that differently to CBH I the C-terminus of the chain is at the core domain and the N-terminus at the tail domain. The sequence of the domains from the N-terminus to the C-terminus is therefore A-B-B -C. B is a repeat of B with strong sequence homologies. The arrow indicates the papain cleavage site.

Figure 7-31 A model for the structure of keratin microfibrils of intermediate filaments. (A) A coiled-coil dimer, 45-nm in length. The helical segments of the rod domains are interrupted by three linker regions. The conformations of the head and tail domains are unknown but are thought to be flexible. (B) Probable organization of a protofilament, involving staggered antiparallel rows of dimers. From Jeffrey A. Cohlberg297...

There are multiple phosphorylation sites in the tail domain of the medium and high molecular weight chain of neurofilaments (NF-H). In the majority of cases, the phosphorylation sites are serine residues within the... 

A good example of a significant species difference is given by the repeats in the tail domain of nestin (an intermediate filament from neuronal cells). In hamsters, the sequence displays 18 consecutive repeats, with each being 44 residues in length. Human nestin, in contrast, was shown to have 22 residue repeats with only 14 in tandem. The sequences of both repeats, nonetheless, showed a close relationship (Steinert et at, 1999b). The 22-residue repeat has an underlying quasi-repeat of just 11 residues (consensus sequence K/E—E—D/N—Q-E—X—L-R/K-X—L—E). 

To facilitate easy access to information, this section has been subdivided (in most cases, purely on the basis of chain type). In a number of instances, however, published data refer generically to both head and tail domains in order not to repeat the information in Sections II.A and II.I, a separate section (Section IIJ) has been written to cover these features. They include (1) the covalent binding sites in head and tail domains that are involved in crosslinks with other proteins in the cell and (2) post-translational modifications and their structural/functional effects in vivo. 

The tail domain in trichocyte Type I chains contains a tenfold P-C-X repeat, seven of them contiguously (Parry and North, 1998). Studies of its likely conformation suggest that it will most likely adopt a left-handed polyglycine II structure with three residues per turn (Fig. 3a). The cysteine residues would thus lie along one edge of the structure, where they would be in positions to form disulphide bonds with cysteine residues in a similar structure from a different molecule. The role of this sequence motif would appear to be that of stabilizing molecular assembly within the IFs. 

Almost nothing is known of the role played by individual amino acid residues in the tail domains of Type III IF proteins. Also, very little sequence regularity has been observed. Nonetheless, the degree of sequence similarity in the tail domains of these proteins suggests that a role analogous to that played by the H subdomains in the keratins is not... 

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