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#core histones

2 public questions tagged with this topic.

Eukaryotic chromatin and chromosome

Which histone has highest evolutionary conservation?

Among histones, H4 shows extreme evolutionary conservation from yeast to humans with only one or two amino acid differences, reflecting severe functional constraint. H4 intimately contacts DNA at fourteen arginine anchor points, participates in H3-H4 tetramer core formation and interacts with neighboring nucleosomes via basic tail binding to acidic patch of H2A. Its N-terminal tail modifications especially acetylation at lysine 16 strongly influence 30 nanometer fiber inhibition and dosage compensation. Mutations in H4 lethal because assembly fails. H1 evolves fastest due to variable C-terminu

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 4: Histone Conservation - H4 Most Conserved

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Eukaryotic chromatin and chromosome

Nucleosome core particle contains how many histones?

Fundamental repeating unit revealed by micrococcal nuclease digestion is nucleosome core particle. High resolution crystallography shows 146 to 147 base pairs wrapped 1.65 left-handed superhelical turns around histone octamer disk. Octamer comprises two copies each of H2A, H2B, H3 and H4, totaling eight proteins organized as central H3-H4 tetramer flanked by two H2A-H2B dimers assembled via histone fold handshake motifs. This assembly induces negative supercoiling, reduces DNA length and provides stability through electrostatic contacts between arginine-rich histone surfaces and DNA phosphate

Ref: Luger et al., Nature 1997, 2.8 Å Nucleosome Core Particle Structure; NCBI Bookshelf, Chromosome Packaging

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