Histones Nomenclature

The above general scheme based on comparisons of the most evolutionarily conserved GHl domain does not reveal the rich microheterogeneity of linker histones which stems from differences between the less well conserved basic tails. Such variants, often referred to as somatic subtypes, occur in plants (for review see Ref. [80]) and animals, both invertebrates and vertebrates (for review see Refs. [81-83]). For example in mammals five somatic subtypes represent the major form of HI HF-1, HF-2, HF-3, HF-4, and HI a, according to the nomenclature proposed in Ref. [82]. The N- and C-terminal tails of the subtypes differ in length, the amino acid composition and the frequency and distribution of phosphorylation sites. The testis specific Hit can be considered the most diverged subtype of the major form. 

Fig. 3. Amino acid sequence of several somatic human histone HI proteins to illustrate the microheterogeneity of linker histones. The sequences for human histone HI variants (H1.1-H1.4) were obtained from Ref [373] and Hl-5 was from Ref [412]. The nomenclature followed for the designation of these histone variants was Doenecke (e.g., see Ref. [412]). The nomenclature of Parseghian et at. [373] is shown in parentheses. The regions corresponding to the trypsin-resistant (winged helix motif [96]) which is characteristic of the protein members of the histone HI family are indicated by a boxed inset.

Fig. 6. Post-translational modifications of core and linker histones. The sites of acetylation, phosphorylation, poly-ADP ribosylation, methylation, and ubiquitination are incficated by numbers that correspond to the amino acid position from the N-termini of the molecules. The nomenclature of histone HI variants is as in Fig. 3. The length of C- and N-terminal tails is in relative scale between core histones to illustrate primary structural differences between these proteins.

Nomenclature Molecular Weight Molar ratio/ FI of Histone... 

Table 9.1 Characteristics of Calf Thymus Histones and Different Nomenclatures Found In the Literature...

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