Archive of Molecular Highlights
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Ubiquitin (Ub) is a 76 residue, highly conserved protein found in all eukaryotic organisms.
Ubiquitin itself does not perform any catalytic, transportative, or structural
function. Rather, it is a signalling mechanism where some other regulatory
mechanism will use it to label a target protein for a particular fate. It is best
known for its role in ATP dependent protein degradation.
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Calmodulin (CaM) is one of the best known examples calcium binding regulatory proteins
in intracellular signalling pathways. Like Ubiquitin, it is highly conserved and abundant in
all eukaryotic cells. As a signalling protein, Calmodulin's function is to bind calcium
ions and then bind a target protein, affecting its activity. It affects processes
ranging from neurotransmitter release to membrane protein organization.
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Lysozyme (Lys) is an enzyme that plays an important role in the prevention of
bacterial infections. It does this by attacking a specific component of certain bacterial
cell walls, peptidoglycan. It was discovered by Alexander Fleming in 1921 when he
demonstrated that his own nasal mucus had the ability to inhibit the growth of a certain
strain of bacteria in culture. In 1966, David Chilton Phillips, using x-ray crystallography,
determined lysozyme's structure, the first ever solved for an enzyme. It has been an
important experimental model ever since.
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Dihydrofolate Reductase (DHFR) is a very important enzyme because
it produces cofactors that are necessary for DNA synthesis. Specifically, DHFR
catalyzes the reduction of folate and 7,8-dihydrofolate (DHF) to 5,6,7,8-tetrahydrofolate (THF).
THF is an essential cofactor involved in the the transfer of methyl, methylene, and
formyl groups from one molecule to another during the production of nucleotides and
several amino acids. An important example of this is the utilization of carbon units
from a THF cofactor by thymidylate synthase to make thymidine nucleotides.
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