CLINICAL CASES
91
[9.5]
E. An inducer is a small molecule that binds to and inactivates a
repressor, which allows the sequence of DNA to be transcribed. An
operon is a set of prokaryotic genes in close proximity that are coor-
dinated as “all off’ or “all on.” An inducer may act to “turn on” the
operon. One classic example is the
lac operon.
When allolactose is
present, it serves as an inducer, and the operon is turned on, allowing
proteins to be formed that metabolize lactose.
B IO C H E M IS T R Y PE A R L S
The synthesis of proteins involves converting the nucleotide
sequence of specific regions of DNA into mRNA
(transcription),
followed by the formation of peptide bonds in a complex set of
reactions that occur on ribosomes
(translation).
Protein synthesis is divided into three stages: initiation, elongation,
and termination.
Ribosomal RNA (rRNA) is a component of the ribosomes, the protein
synthetic factories in the cell.
Many antibiotics take advantage of the differences of the rRNA
between eukaryotic and prokaryotic cells.
REFERENCES
Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell, 4th ed. New York
and London: Garland, 2002.
Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology, 4th ed. New York:
Freeman, 2000.
Petri WA. Anti-microbial agents. In: Goodman AG, Gilman LS, eds. The
Pharmacological Basis of Therapeutics, 10th ed. New York: McGraw-Hill, 2001.
Prescott LM, Harley JP, Klein DA. Microbiology, 3rd ed. Boston, MA: W.C. Brown,
1996.
Voet D, Voet JG, Pratt CW. Fundamentals of Biochemistry, upgrade ed. New York:
John Wiley, 2002.
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