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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 ...
A polyhistidine-tag, best known by the trademarked name His-tag, is an amino acid motif in proteins that typically consists of at least six histidine (His) residues, often at the N- or C-terminus of the protein. It is also known as a hexa histidine-tag, 6xHis-tag, or His6 tag.
Two-component systems accomplish signal transduction through the phosphorylation of a response regulator (RR) by a histidine kinase (HK). Histidine kinases are typically homodimeric transmembrane proteins containing a histidine phosphotransfer domain and an ATP binding domain, though there are reported examples of histidine kinases in the atypical HWE and HisKA2 families that are not ...
In molecular biology, a response regulator is a protein that mediates a cell's response to changes in its environment as part of a two-component regulatory system.Response regulators are coupled to specific histidine kinases which serve as sensors of environmental changes.
Histidine-containing phosphocarrier protein (HPr) is a small cytoplasmic protein that is a component of the phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS). [ 1 ] [ 2 ] The phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS) is a major carbohydrate transport system in bacteria.
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 ...
In terms of enzymology, a histidine kinase (EC 2.7.13.3, EnvZ, histidine protein kinase, protein histidine kinase, protein kinase (histidine), HK1, HP165, Sln1p) is an enzyme that catalyzes the chemical reaction. ATP + protein L-histidine ADP + protein N-phospho-L-histidine.
When histidine charged tRNA levels are low in the cell the ribosome will stall at the string of His residues in block 1. This stalling of the ribosome will allow complementary strands 2 and 3 to form a hairpin loop. The loop formed by strands 2 and 3 forms an anti-terminator and translation of the his genes will continue and histidine will be ...