The classic work of Christian Anfinsen in the 1950s on the enzyme ribonuclease revealed the relation between the amino acid sequence of a protein and its conformation. Ribonuclease is a single polypeptide chain consisting of 124 amino acid residues cross-linked by four disulfide bonds. Anfinsen’s plan was to destroy the three-dimensional structure of the enzyme and to then determine what conditions were required to restore the structure.

The critical observation of Anfinsen that the denatured ribonuclease, freed of urea and b -mercaptoethanol by dialysis;

I. The sulfhydryl groups of the denatured enzyme became reduced by air, and the enzyme spontaneously refolded into a catalytically active form.

II. These experiments showed that the information needed to specify the catalytically active structure of ribonuclease is contained in its amino acid sequence.

III. The 105 wrong pairings have been picturesquely termed “scrambled” ribonuclease.

IV. He found that scrambled ribonuclease spontaneously converted into fully active, native ribonuclease when trace amounts of b -mercaptoethanol were added to an aqueous solution of the protein.

Choose incorrect options;

#Question id: 4064

#Unit 3. Fundamental Processes

Which of the following mutations can result in a reduction of β-galactosidase?

#Question id: 4065

#Unit 3. Fundamental Processes

The NtrC protein from E. coli

a. is a σ54 RNA polymerase.  b. stimulates transcription of the glnA gene.

c. is activated by a protein kinase called NtrB.

d. binds both to an enhancer site upstream of the glnA gene and to RNA polymerase.

e. has ATPase activity.

#Question id: 4066

#Unit 3. Fundamental Processes

Specific DNA control elements in promoters can

a. interact with general transcription factors.

b. interact with repressor proteins. 

c. interact with activator proteins.

d. remain unavailable because of condensed chromatin.

#Question id: 4067

#Unit 3. Fundamental Processes

Reporter genes are used to

a. express enzymes that are not easily assayed in cell extracts.

b. express enzymes that are easily assayed in cell extracts.

c. characterize DNA control elements. 

d. characterize reporter plasmids.

#Question id: 4068

#Unit 3. Fundamental Processes

The three eukaryotic RNA polymerases can be distinguished by

a. the types of genes they transcribe.

b. the number and types of large subunits.

c. their differential sensitivities to cycloheximide.

d. their differential sensitivities to α-amanitin.

#Question id: 4069

#Unit 3. Fundamental Processes

Which of the following can be identified using a series of promoter linker scanning mutations?

a. areas of the promoter that are non-essential

b. areas of the promoter that are essential

c. the presence of separate transcriptional control regions

d. spacing constraints on separate transcriptional control regions