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Histidine ball and stick model spinning. Histidine (symbol His or H) [2] is an essential amino acid that is used in the biosynthesis of proteins.It contains an α-amino group (which is in the protonated –NH 3 + form under biological conditions), a carboxylic acid group (which is in the deprotonated –COO − form under biological conditions), and an imidazole side chain (which is partially ...
The chromosome is ~193 megabases in length. In a 2012 paper, 775 protein-encoding genes were identified on this chromosome. [4] 211 (27.9%) of these coding sequences did not have any experimental evidence at the protein level, in 2012. 271 appear to be membrane proteins. 54 have been classified as cancer-associated proteins.
Histone H4 is a 102 to 135 amino acid protein which shares a structural motif, known as the histone fold, formed from three a-helices connected by two loops.Histone proteins H3 and H4 bind to form a H3-H4 dimer, two of these H3-H4 dimers combine to form a tetramer.
Nucleosomes are portions of double-stranded DNA (dsDNA) that are wrapped around protein complexes called histone cores. These histone cores are composed of 8 subunits, two each of H2A, H2B, H3 and H4 histones. This protein complex forms a cylindrical shape that dsDNA wraps around with approximately 147 base pairs.
The triad is exemplified by chymotrypsin, [c] a model serine protease from the PA superfamily which uses its triad to hydrolyse protein backbones. The aspartate is hydrogen bonded to the histidine, increasing the pK a of its imidazole nitrogen from 7 to around 12. Histidine is thus able to act as a powerful general base, activating the serine ...
Core histones are four proteins called H2A, H2B, H3 and H4 and they are all found in equal parts in the cell. All four of the core histone amino acid sequences contain between 20 and 24% of lysine and arginine and the size or the protein ranges between 11400 and 15400 daltons, making them relatively small, yet highly positively charged proteins. [6]
Direct protein - DNA interactions are not spread evenly about the octamer surface but rather located at discrete sites. These are due to the formation of two types of DNA binding sites within the octamer; the α1α1 site, which uses the α1 helix from two adjacent histones, and the L1L2 site formed by the L1 and L2 loops.
This gene, a member of the histidine triad gene family, encodes a diadenosine P1,P3-bis(5'-adenosyl)-triphosphate adenylohydrolase involved in purine metabolism. The gene encompasses the common fragile site FRA3B on chromosome 3, where carcinogen -induced damage can lead to translocations and aberrant transcripts of this gene.