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Lac repressor - The i gene product of the lac operon is a macromolecular
repressor which, in the active form binds to the operator, thereby blocking
transcription. The repressor also has a binding site for inducer. Binding of
IPTG, allolactose, or some other inducer at this site inactivates the repressor
by vastly decreasing its affinity for DNA. Inactivating the repressor stimulates
transcription
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T7 RNA Polymerase is an RNA polymerase that catalyzes the formation of
RNA in the 5'→ 3' direction. T7 polymerase is extremely promoter-specific
and only transcribes bacteriophage T7 DNA or DNA cloned downstream of a
T7 promoter. The source of the enzyme is the T7 bacteriophage, which is a
virus that infects only bacteria. This phage's polymerase has a very low error
rate.
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Dithiothreitol (DTT) is a reducing agent that is primarily used to protect free
SH-groups from oxidation during the isolation of proteins or other
biochemical procedures. Because of its low redox potential (–0.33 V at pH 7)
DTT is able to maintain free SH-groups in the reduced state and to reduce
disulfide bridges quantitatively. DTT is therefore routinely used in all
laboratories that work with enzymes or proteins. DTT is extensively used in
protein chemistry and in the isolation of enzymes. DTT is more suitable for
the protection of free SH-groups than 2-mercaptoethanol because it forms an
intramolecular disulfide bond on oxidation.
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Lysozyme hydrolyzes β(1-4)-linkages between N-acetylmuraminic acid and
N-acetyl-D-glucosamine residues in peptidoglycans. Gram-positive cells are
quite susceptible to this hydrolysis as their cell walls have a high proportion of
peptidoglycan. Gram-negative bacteria are less susceptible due to the presence
of an outer membrane and a lower proportion of peptidoglycan.
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In biochemistry, PMSF (phenylmethanesulfonylfluoride or
phenylmethylsulfonyl fluoride) is a serine protease inhibitor commonly used
in the preparation of cell lysates. PMSF does not inhibit all serine proteases. It
is rapidly degraded in water and stock solutions are usually made up in
anhydrous ethanol, isopropanol, corn oil, or DMSO. Proteolytic inhibition
occurs when a concentration between 0.1 - 1 mM PMSF is used. The half-life
is short in aqueous solutions (110 min at pH=7 and 35 min at pH=8).[1]PMSF
binds specifically to the active site serine residue in a serine protease. It does
not bind to any other serine residues in the protein. This is a result of the
hyperactivity of that serine residue caused by the specific environmental
conditions in the enzyme's active site.
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A deoxyribonuclease (DNase, for short) is any enzyme that catalyzes the
hydrolytic cleavage of phosphodiester linkages in the DNA backbone.