Attenuation as a control in gene expression.

Attenuation in the tryptophan biosynthetic operon of E. coli.

References: Yanofsky, Nature 289:751 (1981) Read; Genes VI pp374-380

The general structural information shown below was observed from the sequence of the trp operon.

The location of ribosomes determines which alternate secondary structures form.

Other operons controlled by attenuation.

Other Operons Controlled by Attenuation
Operon	Leader peptide
Histidine	MTRVQFKHHHHHHHPD stop
Threonine	MKRISTTITTTITITTGNGAG stop
Ilv (GEDA)	MTALLRVISLVVISVVVIIIPPCGAALGRGKA stop
Leu	MSHIVRFTGLLLLNAFIVRGRPVGGIQH stop
Phenylalanine	MKHIPFFFAFFFTFP stop
IlvB	MTTSMLNAKLLPTAPSAAVVVVRVVVVVGNAP stop

Single-letter abbreviations for amino acids followed by their normal percentage composition in a"average" population of proteins.
Ala = A (8.6)	Arg = R (4.9)
Gly = G (8.4)	Ile = I (4.5)
Leu = L (7.4)	Asn = N (4.3)
Ser = S (7.0)	Gln = Q (3.9)
Val = V (6.6)	Phe = F (3.6)
Lys = K (6.6)	Tyr = Y (3.4)
Thr = T (6.1)	Cys = C (2.9)
Glu = E (6.0)	His = H (2.0)
Asp = D (5.5)	Met = M (1.7)
Pro = P (5.2)	Trp = W (1.3)

An Outside Link to Discussion of Attenuation

Attenuation control of b-lactamase gene expression.

Jaurin et al., Nature 290:221-225 (1981)

Attenuation also controls operons other than biosynthetic ones. One such example is the control of chromosomal b-lactamase in E. coli. This enzyme is regulated by growth rate, the faster the organism grows, the higher the cellular concentration of b-lactamase. The leader RNA sequence upstream of the structural gene for b-lactamase has the following sequence:

Here's what happens to cells when they are exposed to penicillin.