N-terminal tail

Histone phosphorylation is a common posttranslational modification fond in histones, primarily on the N-terminal tails. Phosphorylation sites include serine and threonine residues, tyrosine phosphorylation has not been observed so far. Some phosphorylation events occur locally whereas others occur globally throughout all chromosomes during specific events like mitosis. Histone phosphorylation is catalyzed by kinases. Removal of the phosphoryl groups is catalyzed by phosphatases. 

C-termini and a large glycosylated extracellular loop between transmembrane domains 3 and 4. The proteins show the most homology in their transmembrane spanning domains, particularly domains 1, 2, and 4-8, which may be involved in moving the transmitter across the membrane. The transporters are substrates for PKC-dependent phosphorylation, which reduces their activity. The dopamine transporter is phosphorylated on the extreme end of the N-terminal tail, and consensus phosphorylation sites for various other kinases are present in the intracellular loops and domains [20-22] (Fig. 12-4). The dopamine and norepinephrine transporters form functional homo-oligomers, although it is not known if this is required for transport activity, and the transporters also interact with many other membrane proteins that may control their cell-surface expression or other properties. 

The N-terminal tails of viral fibers are probably unstructured in isolated or expressed fibers, and only assume defined secondary structure when... 

Fig. 70. Domains 2 (cylinders) and N-terminal tails of B- and C-type subunits around the quasi-6-fold axis in tomato bushy stunt virus. The association of the three C-subunit tails around the quasi-6-fold forms domain 1 (see Fig. 84).

Fig. 10.5. Molecular surface of the archaeal (A), the euka otic 20S (B) and the HsIV proteasome (C). The accessible surface is colored in blue, the clipped surface (along the cylinder axis) in white. To mark the position of the active sites, the complexes are shown with the bound inhibitor calpain (yellow). (A) The disorder of the first N-terminal residues in the archaeal a-subunits generates a channel in the structure of the CP, (B) whereas the asymmetric but well-defined arrangement of the a N-terminal tails seals the chamber in eukaryotic CPs. (C) The eubacterial "miniproteasome" has an open channel through which unfolded proteins and small peptides can access the proteolytic sites. (D) Ribbon plot of the free...

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. 

Chopped core particle means nucleosome core particle with the N-terminal tails of core histones removed by tryptic digestion. 

Role of N-terminal tails of nucleosome core histones to the accessibility of small ligands... 

Anderson KC (2004) Transcriptional signature of histone deacetylase inhibition in multiple myeloma Biological and clinical implications. Proc Natl Acad Sci USA 101 540-545 Moore SDP, Herrick SR, Ince TA, Klienman MS, Cin PD, Morton C, Quade BJ, 2000 Uterine Leiomyomata with t(10 17) disrupt the histone acetyltransferase MORF. Cancer Res 61 5570-5577 Morales V, Richard-Foy H (2000) Role of Histone N-Terminal Tails and Their Acetylation in Nucle-osome Dynamics. Mol Cell Biol 20 7230-7237... 

NMR characterization of the recombinant mouse,hamster, bovine and human prion proteins showed that all these molecules share a common architecture, consisting of a flexible unstructured N-terminal tail of about 100 residues from position 23 to position 124 attached to a globular domain within residues 125-228. The globular domain contains a double-stranded anti-parallel /1-sheet and three ot-helices (Fig. 6). 

Fig. 2. The histone octamer. The 3.1 A X-ray diffraction data model of Arents et al. [20] is shown in secondary structure cartoon format. The core of the histone octamer is well defined, but more than 30% of the histone sequence is in regions without secondary structure. These are unfortunately the most interesting regions in terms of epigenetic signaling. 25% of the molecule located in the N-terminal tails (and the C-termini of H2A) in the 3.1 A octamer structure has no interpretable electron density. Despite these limitations, this structure is sufficient to use as a starting model for molecular replacement phasing of the NCP. (Image courtesy of E. Moudrianakis.)...

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... 

---