chapter 32 control of gene expression in prokaryotes

Question 1

…..matching is a recurring theme in protein-DNA interactions

Answer 1

symmetry

Question 2

What motif is common to many prokaryotic DNA-binding proteins

Answer 2

helix-turn-helix

Question 3

helix turn helix function

Answer 3

The first one interacts with the DNA-backbone while the second one is inserted into the major groove of DNA (recognition helix).

Question 4

which enzymes are produced by E.coli when the environment is deprived of glucose and lactose is available? their functions

Answer 4

B-galactosidase (laktos—–> galactose + glukose)
+ galactoside permease (laktose passage through cell membrane)
+ thiogalactoside transacetylase
(detoxification of substances that might come in with lactose

Question 5

How does the lac repressor find its operator DNA

Answer 5

by a one dimensional search

Question 6

The lac repressor

Answer 6

tetramere with subunits that have amino terminals interacting with the DNA and carboxyl terminals contributing the assembly of the protein

Question 7

what is the inducer of lac-operion + and describe it

Answer 7

allolactose. a combination of galactose and and glucose with a-1,6 instead of a-1,4 linkages
a side product of B-galactosidase reaction

Question 8

Which molecules can affect the expression of B-galactosidase without being their substrates?

Answer 8

B-galactosides such as isopropylthiogalactoside

Question 9

how do operon inducers work

Answer 9

work by binding to the lac-repressor and stopping the repressor from binding to the DNA by reducing the dimeric affinity for DNA.

Question 10

Pur repressor

Answer 10

used in pyrimidine and purine biosynthesis

Question 11

what effect does glucose have on genes coding catabolising enzymes

Answer 11

inhibitory effect and its catabolite repression

Question 12

what state of cAMP concentration causes the expression of catabolic enzymes
and the associated protein is called

Answer 12

high

CAP (catabolite activator protein)